Is Zach Thompson the Marlins’ Latest Pitching Success? by Devan Fink July 7, 2021 In late June and in just his fourth major league start, Marlins right-hander Zach Thompson accomplished something that has only been done nine times in the last decade. Facing the Nationals, he went six innings, allowed just two runs (one earned), and struck out 11. In the process, he became the 10th pitcher in the last 10 seasons to strike out 11 or more batters in his first four career appearances — certainly a qualifier-heavy fact, but it still yields quite an impressive list of names: 11 K in Any of First Four Appearances, 2012-21 Pitcher Date Team Opponent Appearance Strikeouts Zach Thompson 6/26/2021 Marlins Nationals 4 11 Freddy Peralta 5/13/2018 Brewers Rockies 1 13 Shohei Ohtani 4/8/2018 Angels Athletics 2 12 Amir Garrett 4/19/2017 Reds Orioles 3 12 Reynaldo López 8/18/2016 Nationals Braves 4 11 Joe Ross 6/19/2015 Nationals Pirates 3 11 Lance McCullers Jr. 6/3/2015 Astros Orioles 4 11 Jacob deGrom 5/31/2014 Mets Phillies 4 11 Chris Archer 9/8/2012 Rays Rangers 3 11 Matt Harvey 7/26/2012 Mets Diamondbacks 1 11 SOURCE: Baseball-Reference As the table shows, it’s rare to break into the major leagues with the level of dominance that Thompson displayed, but his path here has been even more fascinating. In perhaps the most innocuous of moves, the Marlins signed Thompson last November as a minor league free agent to serve as additional bullpen depth. Even still, he was one of the team’s top targets on the minor league free-agent market, Marlins director of pro scouting Hadi Raad told Christina De Nicola of MLB.com, in what he said was based on a blend of scouting and analytics. As Marlins manager Don Mattingly told De Nicola after Thompson’s start against the Nationals, “It’s like, ‘How does this guy get away from teams?’ I liked his stuff, but you never know where that goes, too, after spring training. Sometimes those guys go to Triple-A and you never see them again. Zach, I think, started a little slow, and then kind of got it going. He’s been impressive, so hopefully this just keeps going.” Indeed, following a solid spring training in which Thompson allowed just one run in 5 1/3 innings, he was sent to the minors to function as a potential relief option. (He did get a mention on our preseason Marlins’ Top 46 prospects list, with Eric Longenhagen writing that he “has two average pitches … and 40 control; he’s a fine bullpen depth arm.”) Thompson didn’t immediately pop onto anyone’s radar in Triple-A, but despite a 6.60 ERA, he did post a solid 30.4% strikeout rate in 15 innings and, perhaps more notably, a 2.9% walk rate. He made eight appearances with the Jacksonville Jumbo Shrimp, all out of relief, but minor league pitching coordinator Scott Aldred thought Thompson could be a potential in-house starting pitching option to help Miami deal with the losses of Sixto Sánchez and Elieser Hernandez. That’s exactly what happened; incredibly, Thompson’s first start as a professional in almost four years did not come in the minors but against the Red Sox, back on June 6. Since that debut, Thompson has been one of the best pitchers in baseball, albeit in a small sample. Among pitchers with at least 20 innings since June 6 (and through games on July 5), Thompson’s 32.0% strikeout rate ranks 11th in the majors, and his 24.7% strikeout-minus-walk rate ranks 12th. He’s been worth 0.8 WAR, good for 18th in the majors, and his 2.24 FIP ranks sixth. That’s quite the performance for a 27-year-old who, again, hadn’t made a start in any professional capacity since 2017 and is experiencing his first taste of the majors. And with Sánchez out for the rest of the season after undergoing shoulder surgery, it looks like Thompson’s spot in the rotation is secure for the time being, and perhaps for the rest of the year. So what has led to this immediate big league success for Thompson? For one, he’s shown a collection of five offerings in his first month: cutter (34%), four-seamer (32%), curveball (23%), changeup (6%), and sinker (5%). Judging purely by the fact that he doesn’t throw any one pitch much more than one-third of the time, it’s evident that he’s mixed his offerings well so far. But this can be taken to an even more granular level; for example, he didn’t throw a changeup in any of his first three starts before throwing it nearly 15% of the time in his most recent outing. He’s had success with all five of those pitches, too, with only his fastball (+0.2 runs per 100 pitches) grading out as below-average in terms of run value thus far, per Statcast. By pitch type, here is how Thompson’s results have looked (lower run values are better for pitchers): Zach Thompson, Pitch Results Pitch Usage Run Value RV/100 wOBA xwOBA Whiff% CSW% Cutter 34.4% -4 -2.8 .301 .318 28.6% 35.2% Four-Seam 32.3% 0 0.2 .376 .376 25.0% 27.5% Curveball 22.6% -1 -0.6 .163 .181 50.0% 34.5% Changeup 6.2% -1 -3.1 .000 .456 72.7% 47.8% Sinker 4.6% -1 -8.3 .000 .071 30.0% 35.3% SOURCE: Baseball Savant While there is a lot here that is intriguing, there’s still a ton that we don’t know as a result of small samples. But there is one thing that is super fascinating: Thompson’s cutter might already be one of the best in baseball. There have been 113 pitchers to throw at least 50 cutters in 2021, and Thompson’s 35.2 CSW% shot straight to the top of the leaderboards. He’s tenth among all pitchers, and is fourth — behind only Dustin May, Corbin Burnes, and Trevor Bauer — among starters: Best Cutter CSW%, SPs Player Cutters CSW% Dustin May 68 44.1% Corbin Burnes 673 38.0% Trevor Bauer 386 36.0% Zach Thompson 128 35.2% Yu Darvish 633 34.6% Charlie Morton 166 33.7% Eduardo Rodriguez 273 31.5% Kyle Gibson 195 30.8% Joe Musgrove 280 30.4% Dean Kremer 180 30.0% Among starting pitchers with at least 50 cutters. Being in the realm of Burnes, described on this very website as owning baseball’s best cutter, and Darvish, who has earned that title elsewhere, is very exciting for Thompson fans like myself. What is particularly interesting about Thompson’s cutter is that it possesses quite a bit of seam-shifted wake. This phenomenon, which has been detailed by both Christian Hook at Driveline Baseball and Ben Clemens here at FanGraphs, may at least partly explain why it has been so effective. On his blog, Tom Tango did a quick study on the impact of seam-shifted wake on pitch type effectiveness, concluding, “By far, the cutters with the most SSW are the most effective, and those with the least amount of SSW are the least effective.” Considering Thompson has some of the most seam-shifted wake in baseball on his cutter, it might not be a surprise that hitters have struggled to square it up. Among the 113 pitchers to throw at least 50 cutters this year, he has the 19th-largest difference in movement versus inferred movement based on his release. You can see that from these two images here: On the left is Thompson’s spin-based movement, and on the right is his observed movement. For his cutter, his average spin-based movement is at 12:00, but his average observed movement is at 10:45. This +1:15 change is one of the most significant among all cutters. This doesn’t necessarily mean that he is generating significant horizontal break on the pitch (he’s actually not getting that much more than average); rather, it means that the break he does generate comes late in the pitch’s flight, making his cutter dart away from hitters at the last possible second. Take this pitch to Joc Pederson, for example. Thompson’s cutter doesn’t have insane movement in and of itself, but the pitch moves away from Pederson’s bat at the best possible time: Just because Thompson’s cutter might have a lot of seam-shifted wake doesn’t necessarily mean that it’s going to continue to have success into the future. But based on what we know from Tango’s findings — as well as the early returns on Thompson’s pitch — it seems likely that this amount of late movement is one of the keys to his hot start to his major league career. What does that mean for the rest of Thompson’s season, let alone the rest of his time in baseball? It’s still too soon to tell. But for a team that already has a lot of young and exciting pitching, the Marlins may have found a potential diamond in the rough.