This a guest post completed by Josiah Rutledge, be sure to follow him on twitter.  We here at Innings Pitched are excited about his work and hope he can find the time to become a regular contributor. 

Below are basic scouting reports for two pitchers. If you read the title of this article, you probably know where this is headed, but hear me out anyway.

Pitcher A, a left-hander with an extremely high arm slot, averages 94 mph on his fastball, which he relies on heavily, throwing it nearly three quarters of the time. His primary offspeed pitch is a sharp power curve in the low 80s. His rarely used changeup flashes good movement with a mediocre velocity gap. His control isn’t terrible but is definitely below average.

Pitcher B, also a lefty, throws even harder than Pitcher A, and is averaging 97 mph on the heater from his three-quarters slot. Though he throws extremely hard, he relies on it only slightly more than a typical hurler. Instead, his out pitch is a cutter, of the “baby slider” variety that ranked as one of the best pitches in the game by whiffs and grounders. His third pitch is a sharp curve that averages 82 mph and has the most drop of any 80+ mph curve. He also throws a changeup with a decent velocity gap, plus fade and plus drop, but it’s his fourth pitch so is used sparingly. His control is great, as his BB% would’ve been sixth best in the game had he qualified.

In case you haven’t caught on:
Pitcher B is James Paxton of the Seattle Mariners.
Pitcher A is…also James Paxton, prior to last year.

There are some similarities between the scouting reports (hard-throwing lefties, sharp curveballs and changeups with good movement), but there are a whole lot of differences, especially considering we’re talking about the same guy. Even the similarities, when you look a little deeper, had some key changes.

Speaking of looking a little deeper, let’s do a bit of that with six changes I’ve highlighted – some big, and some small:

Pitching Mechanics, Change in Arm Slot

James Paxton Seattle Mariners Pitching Mechanics Release Points

James Paxton, Seattle Mariners, Release Points

That’s Paxton’s horizontal release point on the left (moving nearly a foot towards first base) and his vertical release point on the right (dropping about seven inches).

Baseball pitchers make mechanical changes all the time. They’re rarely as dramatic as an entirely new arm slot. Those charts certainly show how drastic the change is, but let’s leave the charts behind for a moment and take a look at some good old-fashioned photographic evidence:

James Paxton Seattle Mariners Arm Slot

James Paxton Pre-2016 Arm Slot vs 2016 Arm Slot

That may not look like much, but it’s a dramatic* difference. In the first picture, Paxton’s elbow is slightly above the top of his head, however in the second picture his elbow is even with his earhole (refer to yellow lines).

In his old delivery, if you drew a line straight down from his elbow it would run into his hip, while in the new delivery it would be nearly a foot away (refer to red lines).

Those differences in where his elbow is, lead to even bigger differences in where he releases the ball (remember, a small change in angle adds up fast over distance). Using the distances from the release point chart above and doing some basic geometry (thanks Pythagoras!) shows us that Paxton’s release point changed by about 14 inches.

*Side note: I’m using the words “dramatic” and “drastic” a lot. I may sound like a broken record with those words, but there really isn’t another way to describe the changes James Paxton has made.

What about the rest of his pitching mechanics? Surely a pitcher cannot completely change his arm slot without some other changes, right?

Let’s do some side by sides of various points during his delivery and see what differences we can spot.

“Old” James Paxton on the left and “new” James Paxton on the right.

James Paxton Seattle Mariners, Pitching Mechanics

James Paxton 2015 vs 2016 Chin Tuck

So far…no noticeable difference in his windup.

A small, controlled step back towards third base and his chin tucked towards his chest.

Let’s keep looking. Next up, the top of his leg kick:

James Paxton Seattle Mariners Leg Kick

2015 Leg Lift vs 2016 Leg Lift

Still very, very similar. Moving on to the next shot, as Paxton pushes off towards home:

James Paxton Seattle Mariners Leg Stride

2015 vs 2016 Glove Side Action

Finally, we can start to see the changes that led to the extreme changes those graphs showed us.

I’ve noticed that pitchers’ release points tend to mimic where the points of their heads (and, to a lesser extent, their gloves) are at right before their arm starts to come forward.

That could not be more true with Paxton.

As we saw in the graphs at the start of this section, his release point moved both down and towards first base. In the pictures above, we see his head and glove do the exact same.

His glove used to point nearly straight up, now it points nearly straight at the first base dugout. The change in position of his head and glove almost exactly mimics the change in his release point.

Let’s see what kind of chain reaction that change creates in the rest of his delivery:

James Paxton Seattle Mariners Upper Body Mechanics

2015 vs 2016 Upper Body Mechanics

Ignore the blurriness of the photos…isolating his upper body from available video sources can be a tricky measure.

Both pictures are freeze frames as his foot hits the ground.

You’ll notice that in the first picture (old delivery) his chest is still nearly perpendicular to home plate. While in the second (new delivery) he’s started his trunk rotation; his chest is beginning to face the plate, his arm has already come out of the scapular load and is beginning to come towards the plate.

In James Paxton’s old delivery, he had a severe timing problem, with his upper body significantly behind his lower body, causing his arm to drag. I believe this capped his velocity and caused excessive stress on his shoulder and arm, leading to problems with his lat (the muscle right below the shoulder) that landed him on the DL.

That issue is mostly fixed in his new delivery, as his arm is coming forward as his foot hits the ground. Ideally, I’d like to see his arm a bit farther forward at this point, but it’s no longer a glaring timing issue, and as a result I’m less worried about his timing causing him injuries.

While the arm slot is the obvious change, I’m convinced that the timing issue is the more impactful change. For Paxton, however, the changes are obviously tied to each other.

While baseball pitchers with three quarters arm slots are not intrinsically more or less likely to have timing issues, it’s clear that Paxton’s switch has helped him alleviate his timing issues. It is my belief that this unlocked a couple extra ticks of velocity for Paxton (more on that in the next section), and that it will help him overcome the durability issues that have plagued him in the past.

Better Pitching Mechanics, Increased Fastball Velocity?

Both versions of Paxton throw hard. Very hard, in fact. In 2015, Paxton had the third fastest average four-seam velocity among left-handers, according to Baseball Prospectus’ PitchFX leaderboard. James Paxton was never lacking when it comes to bringing the heat.

Paxton’s already elite velocity made it even more surprising when this happened:

James Paxton Seattle Mariners Four Seam Fastball Velocity

Career Four Seam Fastball Velocity

Yep, that’s a spike of nearly two full ticks, which ranked among the biggest spikes in baseball. The spike took Paxton from a hurler with elite velocity to a hurler with off the charts velocity – he averaged two full miles per hour faster than the next hardest throwing lefty, and only noted flamethrowers Noah Syndergaard and Nathan Eovaldi had higher average fastball velocities among starters.

The following bar graphs demonstrate just how dramatic that velocity increase really is:

James Paxton Seattle Mariners Four Seam Fastball Velocity Curves

2013 to 2015 vs 2016 Velocity Curves

The most noteworthy item on the graph is that, for the first time in his career, James Paxton touched triple digits, throwing exactly one pitch at 100.8 mph. Another career first: he did not throw a fastball below 90mph. So he improved both his maximum and minimum velocity.

He also showed a lot of improvement in between, as you might’ve guessed.

You might notice that the graphs show the same shape, and that it’s similar to a standard distribution. But you also probably noticed that the distribution shifts over two spots to the right – as we saw earlier, his average velocity jumped from 95.1 to 97.4 mph, which equates to two spots on the graph.

Despite throwing ~600 less fastballs in the graph on the right, he nearly quadrupled the number of 97+ mph pitches. Earlier in his career, he sat in the 92-96 mph range, and now he’s sitting at 95-98 mph.

Obviously, all things being equal, throwing 97 instead of 95 is an improvement. But, the point of this article is that all things are most certainly not equal for Paxton, so what else changed with his fastball.


James Paxton Seattle Mariners Four Seam Movement

Career Four Seam Fastball Movement

I’m not going to lie, when I first saw those graphs I was certain I had accidentally pulled up the release point graphs instead. Nope…these ones also look like that.

How many identical looking graphs can one pitcher produce?

In the graph on the left (vertical movement), we see that James Paxton had been steadily adding rise to his fastball, but last year his fastball went from the upper quartile in rise to having the fourth most sink of any lefty starter. Interestingly, this didn’t lead to an increase in groundballs on the fastball – his groundball rate on the pitch actually declined slightly, and he got slightly more pop-ups, due to throwing the pitch higher in the zone.

Perhaps the more important change is the horizontal movement, which went from perfectly middle of the pack to among the elites – especially impressive given that Paxton’s extreme velocity gives his pitches less time to move.

Unsurprisingly, the increase in fade, switching to sinking instead of rising and (especially) the increase in velocity led to a spike in whiffs on the pitch (from a 4.6 SwStr% in 2015 to an 8.3 SwStr% in 2016).

While the velocity is the change that gets all the headlines (and rightfully so), the movement is every bit as extreme of a change. Boy is this pitch different than it was!

Better Pitching Mechanics, More Control?

Are you ready for another graph that falls off a cliff?

James Paxton Seattle Mariners, Walks Per Nine

Career Walks Per Nine Innings

That’s Paxton’s seasonal BB/9 rates. You can largely ignore that first year as it came in only 24 innings and be posted a 3.58 BB/9 in 145.2 AAA innings that year.

Paxton 1.0 owned a career 9.4 BB%, which isn’t absolutely atrocious but is certainly a concerning rate of free passes.
Paxton 2.0 cut that number in half, posting a 4.7% BB rate that would’ve ranked sixth in baseball, had he qualified. John Trupin put it best over at Mariners blog Lookout Landing:

“Paxton went from a tall lefty trebuchet to a Robin Hood-esque marksman.”

I can’t top the coolness of that sentence, but perhaps I can provide some additional insight:

(By the way, with the extreme over the top nature of his old delivery and old glove action, he really did look like a trebuchet.)

First off, obviously it’s easy (and quite likely correct) to attribute much of his control gains to his change in pitching mechanics. Even if one delivery wasn’t necessarily superior by itself, it’s clear that Paxton has a much better feel for and much better control over his new delivery than he ever did over the old one.

While his approach certainly changed, as he upped his F-Strike% by nearly nine percentage points and his Zone% by nearly four, I don’t think we can attribute all of the decrease in walks to simply not nibbling anymore – to do so would sell short the actual command gains Paxton made.

Consider: in 2015, 16.3% of his pitches in the zone were in the middle-middle section (where the middle third vertically and the middle third horizontally intersect), but in 2016 that number fell to 13.0%. He wasn’t following what I think of as the Michael Pineda School of limiting walks: “just throw it down the middle and if you miss it’ll still be a strike”.

No, Paxton showed true gains in his ability to hit his spots. Using Bill Petti’s Edge%, we can see that Paxton’s gain in Zone% came solely through an increase in hitting the corners, as his Edge% went up 5.4 percentage points while his Heart% increased only half of a percentage point. A combination of an increased willingness to pound the zone and an increased ability to do so without throwing meatballs, led Paxton to soar from a below average control guy to one of the elite limiters of the free pass in the game (a Robin Hood-esque marksman, as Trupin put it).

What Is This, A New Out Pitch?

Prior to 2016, Paxton’s cutter was a scarcely used piece of his arsenal that returned below average results, (1.3 runs below average over only 65 pitches) despite having the element of surprise whenever he did throw it. In 2016, as I mentioned earlier, it was one of baseball’s best pitches.

So what happened? How did it go from nearly nonexistent to a truly dominant out pitch?

For one thing, the cutter started looking like this, which is good:

James Paxton Seattle Mariners Cutter

New and Improved Cutter vs. Mike Trout

The cutter’s horizontal movement stayed very similar to earlier incarnations, but he added more than three inches of drop, giving his cutter the third most drop of any in the game – and the most of any lefty. It got whiffs 19% of the time, double the league average. Not only did he lead the league in swinging strike rate on the cutter (by two full percentage points), he actually led the league by fair margins in both whiffs per swing and swing rate.

Those insane whiff rates weren’t just the result of the velocity and movement on the pitch.

Check out the location:

James Paxton Seattle Mariners Cutter Pitch Location

2016 Cutter Location

That’s impeccable command that would help any pitch play up, let alone one with the nastiness of Paxton’s cutter. Paxton clearly had a plan with it (throw it glove-side) and executed remarkably well. The combination of velocity, movement and command took his cutter from an afterthought (and a poor one at that) to one of the game’s truly elite offerings.

Obviously, a pitcher adding a new pitch is always something to consider (because of how different it is and how rarely he threw it before, I consider this cutter a “new pitch”). Adding a good pitch is obviously a huge thing – it was a big part of what took Jacob deGrom from non-prospect to ace. But what about adding a new pitch that immediately becomes one of the best in the game?

That’s pretty unheard of.

What About His Old Out Pitch, The Knuckle Curve?

As a prospect, Paxton’s knuckle curve was his calling card – the pitch that was going to take him places. It didn’t disappoint on reaching the majors, posting elite whiff rates every season.

But Paxton didn’t just leave it be while everything else in his arsenal changed:

James Paxton Seattle Mariners Curveball Movement

Career Knuckle Curve Movement

Okay, this is getting ridiculous.

Why does every graph look the same?

If I didn’t know better I’d say someone was pranking me.

But no, James Paxton really did do that. He added nearly three inches of drop over last year and nearly three and a half inches of glove side break. That’s four and a half inches of difference between his 2015 curve and his 2016 curve!

Movement numbers for curveballs sometimes don’t tell the whole story. A sharply breaking curve with slightly less movement is worth much more than a loopy curve that can be picked up quickly out of the hand. Thanks to Statcast, we can now measure the spin rate in RPMs of each pitch, giving us a nice proxy for a curveball’s sharpness.

From 2015 to 2016, Paxton’s curveball spin rate increased by about two hundred RPMs, which shows that the increase in movement did not come from making the pitch loopier – no, he sharpened it.

Based on movement, velocity and spin (not to mention becoming his third pitch instead of second), we would expect this pitch to perform even better than it had in the past. Yet his whiff rate declined and the batting average and slugging against the pitch increased (though both were still well above average). If he can better harness the improvements, the curve can potentially be a second dominant off-speed pitch along with the cutter.

You like the sound of that? I do too.

James Paxton’s Changeup

The final piece to Paxton’s arsenal is his changeup. Though it was clearly his fourth pitch and he threw it only eight percent of the time, it got the most whiffs per swing (44.3%) of any of his pitches and posted an excellent 17.4% swinging strike rate. Among starting pitchers who threw at least 100 changeups, only Jake Arrieta, Jeremy Hellickson and Stephen Strasburg posted better Whiff/Swing numbers. That’s impressive company.

How did Paxton, a pitcher never known for his changeup, develop one so dominant? Well:

James Paxton Seattle Mariners Changeup Movement

Career Changeup Movement

While these graphs have the massive cliff and massive spike, respectively, that you’ve come to expect from the graphs in this analysis, I want to point out something related to the vertical movement graph: this isn’t the first time Paxton has added sink to his changeup (though it is a far bigger difference than from 2013 to 2014). It’s no coincidence that, when you graph his whiffs per swing on the changeup, you see the exact opposite shape you see in the vertical movement graph:

James Paxton Seattle Mariners Whiffs Per Swing

Career Changeup Whiffs Per Swing

It’s easy to see the correlation here. The more his changeup sinks, the harder it is to hit. That was true when he added sink in 2014, and it was true when he added even additional sink (2.5 inches more than 2015 and almost four inches more than 2013).

That’s intuitive: with the exception of the “rising” fastball, more drop on a pitch is generally a good thing – the more movement the better. See Innings Pitched post explaining the rise of the fastball and the magnus effect to learn more.

Speaking of more movement, take another look that horizontal movement graph – he added another inch of fade to the change. Here’s a nice example of his “new” changeup that gets Devon Travis so far out in front his bat goes flying into the stands:

James Paxton Seattle Mariners Changeup

Devastating Changeup to Devon Travis

You can see that he gets solid sink on the pitch. There’s some fade here, but nothing mind boggling. He also has a good not great velocity difference (about 9 mph). Based solely the changeup’s movement, we’d expect the pitch to be average to slightly above average.

How’d he post an elite whiff rate, then?

A combination of factors, I would propose: first, the elite velocity of his fastball forces hitters to gear up for it, making them especially vulnerable to changes of speed. Second, the fact that he uses it relatively infrequently gives it an element of surprise when he does throw it. Third, his arm angle means his other pitches (particularly the fastball) are slung across his body and coming slightly towards the batter, which amplifies the fading effect of the change. The means the batters expect it to continue towards them, and instead it begins to fade away. That third factor is amplified by the fourth – his ability to locate the pitch to the arm side and down.

James Paxton Seattle Mariners Changeup Heatmap

Changeup Heatmap Per Baseball Savant

In my opinion, James Paxton’s changeup is a case of a decent pitch in a vacuum performing like a fantastic one due to context. While I expect some regression off his best-among-lefties Whiffs/Swing ratio, it’s good enough to be a quality pitch and a phenomenal fourth pitch – and I may well be underrating it.

The Epic Conclusion

There’s one thing that baseball analysts and writers are constantly reminded of, and yet they still seem to forget: players change.

A player’s production is rarely static from season to season, and though some of that variation can be attributed to chance or to circumstance, often it comes from actual skill changes – sometimes for the better, sometimes for the worse.

It’s clear that, in Paxton’s case, there have been substantial skill changes. All four of his pitches, his mechanics, and his command underwent drastic changes – that’s almost unheard of.
Here’s the scary part: Paxton 1.0 was pretty good, owning a 3.16 ERA and a 3.70/3.80 FIP/xFIP over 30 starts, though he had a tendency to land on the DL. All of the changes he has made are fundamentally good changes – better mechanics, more velocity, more movement, better command.

Though there were some growing pains as he adjusted to his new arsenal (he got lit up on grounders, allowing a .300 AVG and the second highest exit velocity in the league), he turned it around down the stretch, posting a 3.19 ERA, a 2.45/2.99 FIP/xFIP, a 9.4 K/9 and a 1.2 BB/9 from July 22nd onwards.

If Paxton can continue to hone the usage of his overhauled arsenal, he could become the ace many scouts dreamed he would. I consider him a dark-horse candidate for the AL Cy Young – and honestly, I don’t think it’s much of a stretch.