by 
The Reds selected Tyler Mahle in the 7th round of the 2013 draft at the age of 18. The young right-hander, who played high school ball less than an hour from Dodger Stadium, worked his way through the Reds organization at a brisk pace. At age 20 he pitched for A-Dayton, at 21 for A+ Daytona and AA-Pensacola. In 2017, he made about a dozen starts for Pensacola then AAA-Louisville before getting a call-up to the Reds for four starts in August and September.
You remember 2017. The Reds lost 94 games under Bryan Price and the organization was a wasteland for pitcher development. The Reds gave 20+ starts to Tim Adelman and Scott Feldman and devoted 14 to Bronson Arroyo’s farewell tour. Remember now? Lisalverto Bonilla, Asher Wojciechowski, Jackson Stephens, Rookie Davis and Brandon Finnegan got four starts. Deck McGuire got two.
Walt Jocketty handed out starts like Oprah gave away cars. Hey you, the batboy, you get a start!
Tyler Mahle’s major league debut took place amid that calamity. He pitched 20 innings in 2017, struck out 14 and walked 11. At age 22.
2018 was Mahle’s first full major league season, making 23 starts for the Reds, but only one in August and September. In 2019, Mahle was in the rotation all year except for missing August with a hamstring pull. Even though Mahle, still just 24, had showed improvement, the Reds signed Wade Miley before the 2020 season and the lefty veteran was anointed the fifth starter in January. But injuries to Miley gave Tyler Mahle the opportunity to start nine games in 2020.
Tyler Mahle’s breakthrough 2021
In 2021, at the age of 26, Tyler Mahle is having his best season. If you need proof of that, check out the metrics that most isolate the role of the pitcher himself. Strikeouts and walks are among the oldest stats in baseball. xERA eliminates the effect of stuff pitchers can’t control: defense, park dimensions, relief pitchers, official scorers and luck on balls in play. xFIP takes it a step further and minimizes the role quality of contact plays.
No matter how modern of a measurement you prefer, Mahle has been better in 2021 than ever before.
That, of course, leads inquiring minds to ask: What’s going on? Is Tyler Mahle throwing the ball harder, with more spin, getting more movement? Has he changed his pitch portfolio? Are there particular batters he’s having better success against?
When you dig through the data, one fact jumps out.
All of Tyler Mahle’s improvement in 2021 has come against left-handed batters.
This chart that looks at Mahle’s xFIP splits for left-handed hitters (LHH) and right-handed hitters (RHH) shows exactly that. Mahle’s right-handed split hasn’t changed much in 2021. He’s always been terrific against righties, with an xFIP right around 3.50 or below. What’s changed is on the other side of the plate.
Prior to 2021, Mahle had struggled mightily against lefties. His xFIP was around 5 or, gulp, even higher. That’s no longer the case.
If graphs resonate more with you than charts, here you go. 
Notice how the blue line (LHH) is higher than the red line (RHH) for the years 2017-2020. Much higher. Two runs or more higher. But in 2021, the two lines converge. The red line has stayed flat while the blue line (LHH) shows a steep drop. That shows all of Tyler Mahle’s improvement in 2021 has come against left-handed batters.
Don’t write off success against left-handed batters as unimportant because only a quarter of major league hitters bat from that side. Opposing managers have stacked their lineups against Mahle. 48% of the 350 batters he’s faced this season have stood in the left-handed batter’s box.
Now that we’ve pinpointed Mahle’s 2021 improvement as coming against southpaws, what’s behind it?
This question has a simple answer, too. It’s his four-seam fastball.
vs. LHH; DNT = Did Not Throw
The fastball has always been Tyler Mahle’s primary pitch. Early in his major league career, Mahle was known for it. It was said his command of that one pitch was what got him to the majors. Mahle threw it for two-thirds of his pitches in 2017 and 2018. His fastball usage rate has declined over the years as Mahle added a splitter to his breaking pitches, but he still throws his fastball 51% of the time in 2021.
But what is it about his fastball that’s been better? The vertical and horizontal movement hasn’t changed since last year, so we can rule out spin-rate or grip (or sticky stuff). No, Mahle’s new fastball formula vs. lefties is location, location, location. He’s throwing the heater inside.
Tyler Mahle has always been an up-in-the-zone guy with his fastball. Here’s the heat map for every four-seamer he’s thrown for the Reds, to both RHH and LHH. You can see the center of frequency is closer to the top of the strike zone than the bottom.
Mahle all Fastballs (2017-2021)
Prior to 2021, Mahle had pitched lefties up high with his four-seamer, but also a fair amount down and away. This heat-map shows it:
Mahle Fastball vs Lefties (2018-2020)
You can see the two clumps of red. From 2018-2020, Mahle worked his fastball to lefties to two locations. He kept a large number up in the zone, as he had done with all batters. But he also threw down and away, as you can see with the clump of red down and to the left — away from the left-handed batter.
But in 2021, Mahle has changed his fastball approach. Tyler Mahle is busting lefties inside.
Mahle Fastball vs. Lefties (2021)
Notice the absence of the down-and-away pitch to left handed hitters in 2021. And in 2021 Mahle hasn’t exclusively relied on the ball being up in the zone. Yes, he still throws it more up than down. But compared to previous seasons, his fastball isn’t as concentrated at the top.
A couple videos from this season demonstrate his success with it. In the first, Mahle strikes out the Giants’ Brandon Belt on a high, inside 96-mph fastball.
In the second example, Mahle punches out Cardinals rookie Dylan Carlson on an inside 95-mph fastball.
Notice on that pitch how Tucker Barnhart called for it middle-high, not at the top of the zone. That’s where Mahle delivered it.
This graph is his xwOBA on fastballs just to left-handed hitters. xwOBA is a composite stat that accounts for strikeouts, walks and quality of contact as measured by launch angle and exit velocity. If you’re going to look at one stat to see how a pitcher has been doing, xwOBA is about the best there is. League average xwOBA has been.313-315.
Prior to 2021, Mahle has had trouble with his fastball against lefties, with his xwOBA way above average. But this year, his xwOBA is way better than league average, at .219.
Through his first 16 starts of the 2021 season, Tyler Mahle has confronted his biggest weakness as a pitcher — getting out left-handed hitters. He found the solution in the pitch he’s always thrown the most.
Conclusion
Tyler Mahle will make his 17th start of the season tomorrow afternoon against the Cubs. He’s pitching in his first arbitration season, making $2.2 million. If not signed to an extension, Mahle will become a free agent in 2024.
With each new start, the 6’3″ right-hander is proving his worth as a long-term investment. The significant improvements he’s made in his pitch arsenal and location are putting on display what the Reds saw when they called him up in the fall of 2017. He’s become a solid pillar of the rotation.
The Reds should try to work out an extension with Tyler Mahle. But the price tag goes up with every inside fastball he zips past a left-handed batter.
Photo: Rick Ulreich (Icon Sportswire) batter.
He has shown some serious dips in spin rates over the past couple starts, and he seemed to not be as effective. Does that worry you for his future if even sunscreen and rosin are not allowed?
It’ll take more time to tell. Mahle’s spin rates started dropping at the end of May. Since then, two of his three pitches have had better xwOBA and the third has been about the same. This post only looked at his fastball. Since his success has been due to location and not movement or velocity, spin rates could be less important. If he’s not as concerned with keeping it up in the zone against lefties, again spin rates would be less important.
You’re right that his spin has come down noticeably, but it’s too soon to tell what, if any, effect it will have on his success.
Great stuff. Thanks, Steve. I hope they sign a big extension with Tyler.
I’m nervous about signing a pitcher to a long-term deal after Homer Bailey. Am I nuts to prefer a trade for lots of prospects in the walk year?
Not a long-term deal. Just add a year or two to his current time with the Reds. Like the Reds did with Cueto for his extension.