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James Paxton’s pitch tunnels may explain his platoon splits

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James Paxton has struggled against left-handed batters this season. Let’s try and find out why.

Seattle Mariners v Baltimore Orioles Photo by Mitchell Layton/Getty Images

Since his breakout year in 2016, James Paxton has quickly established himself as one of the premiere pitchers in the American League. This season, he’s continued to improve. He’s striking out almost a third of the batters he’s faced and has already thrown a no-hitter. By most metrics, he’s been better than ever. But digging a little deeper reveals something a little concerning. His performance against left-handed batters isn’t what you’d expect. From 2016 to 2017, left-handed batters posted a .262 wOBA against Paxton but that mark has jumped up to .405 this season. What gives?

In his article yesterday, Tim examined the Mariners embrace of cutting edge technology to improve player performance. He referenced this piece from SportTechie throughout. Paxton, among others, has really benefitted from this use of technology, specifically using Rapsodo pitching monitors to glean as much information about his repertoire as possible.

Paxton said he used Rapsodo in spring training to learn more about a pitching concept called “tunneling”—essentially, a pitcher tries to start different pitch types down the same path, or tunnel, so a hitter has trouble discerning which has actually been thrown. He seems to have paired his two premium pitchers, his fastball and curveball, with devastating effect. So far this season, Paxton has thrown significantly more fastballs in the upper part of the strike zone; high fastballs and diving curveballs are known to be a great combination because they both begin their plate-ward journey on the same plane.”

YES! I’ve explored pitch tunneling a few times this year. If you’re unfamiliar with pitch-tunneling, it’s a fairly easy concept to grasp. The argument goes that a pitcher is far more effective if he can mask the movement of his pitches as long as possible, reducing the time batters have to recognize the pitch type. We also know that pitch-tunneling is linked to a repeatable delivery and pitch location.

For Paxton, creating effective pitch tunnels is a recent development. He famously adjusted his arm angle in 2016, helping him reach the awesome velocity he now possesses. But like with any adjustment, he’s struggled with consistency from time to time. Two years removed from that change, it looks like he’s finally found the consistent release point to create an effective pitch tunnel. And like the SportTechie article mentions, pitch location also plays a significant role in creating effective pitch tunnels. Paxton has used the high fastball to great effect this season.

What does the actual pitch tunneling data tell us? Using Pre-Tunnel Maximum Distance (PreMax), which is defined as, “the distance between back-to-back pitches at the decision-making point,” we can see just how effective his fastball-curveball pitch pair has been.

James Paxton Pitch Tunnels (2016-2018)

Batter Hand Pitch Pair PreMax - 2018 PreMax - 2017 PreMax - 2016
Batter Hand Pitch Pair PreMax - 2018 PreMax - 2017 PreMax - 2016
RHB Fastball-Curveball 1.37 1.40 1.60
LHB Fastball-Curveball 1.70 1.69 1.66
RHB Curveball-Fastball 1.53 1.53 1.61
LHB Curveball-Fastball 1.85 1.34 2.02
The league average PreMax across all pitch pairs was 1.54 inches; a smaller PreMax value is better.

Against right-handed batters, Paxton’s fastball-curveball pitch tunnel is better than ever. That’s certainly one of the reasons why they’re posting a .255 wOBA against him this season. But against left-handed batters, that same pitch pair has become much easier to discern. And it’s his fastball that they’re keying in on. Lefties are batting .366 off his fastball and it looks like it’s because they’re able to distinguish that pitch from his curveball, particularly when he throws his bender first. Perhaps his significant platoon splits are also related to his pitch mix. When left-handed batters are ahead in the count, he turns to his fastball 80% of the time.

Looking at his pitch heatmaps against left-handed batters, it looks like he’s locating his curveball down and out of the zone and his fastball up and in a little more often.

Fastball location vs. LHB:

2017 on the right, 2018 on the left.

Curveball location vs. RHB:

2017 on the right, 2018 on the left.

Those locations would normally be a good thing but perhaps that change in location is affecting his pitch tunnels more than he wanted. Last season, he located his fastball almost exclusively on the outer half of the strike zone against lefties and his curveball found the zone a little more often. It may seem weird to suggest locating his breaking ball in the zone more often but perhaps that would help him create that deception he’s been lacking this year. Or maybe he needs to locate his fastball on the outer half of the zone when sequencing it with his curveball.

Whatever the case may be, it’s encouraging that Paxton is using all of the data at his disposal to continue to improve. Now he needs to make some adjustments to his approach to continue to maximize his repertoire.