Trevor Williams Is Staging a Comeback

This is Chet’s first piece as a FanGraphs contributor. He believes data is the most compelling storyteller and loves using analytics to attempt to demystify the game of baseball. He previously covered the Colorado Rockies for Purple Row. A graduate of Georgia Tech, he had the opportunity to participate in Danny Hall’s walk-on tryout in 2003, though he apparently failed to blow the legendary coach away with his 76 mph fastball. Chet lives in Lakewood, Colorado with his wife and two children, all of whom tolerate way too much baseball talk at the dinner table.

Trevor Williams headed into spring training at a pivotal moment in his career. Following two solid seasons of work in the Pirates’ rotation, he experienced a somewhat delayed sophomore slump in 2019. His performance declined significantly. He finished the season with an ERA of 5.38 and a FIP of 5.12 both more than a run higher than the average from the previous two seasons. His campaign to bounce back in 2020 never took off and he ended up on the wrong side of the small sample coin flip, ending the year with a 6.30 FIP and -0.4 WAR, career lows. He was designated for assignment in November.

Fresh off trading their former ace, Yu Darvish, the Chicago Cubs scooped Williams up on a low-risk, one-year deal for $2.5 million. From the Cubs’ point of view, the upside is clear. While Williams has had an awful go of it recently, he is only 28 years old and was once a capable fixture in a major league rotation. Williams (in the parlance of our times) shoved throughout spring training and earned himself the position as No. 4 starter in the Cubs’ rotation, but the question remains as to whether or not he can perform as he once did in 2017 and ’18.

Let’s rewind the tape a bit. Williams had a brief cup of coffee (one start and 12.2 total innings) in 2016 before starting the ’17 season in Pittsburgh’s bullpen. In the season lead-up, our own Eric Longenhagen had this to say of Williams:

“A lead-armed sinkerballer who dominated the International League with a low-90s fastball/sinker combo that he’d run up to 94, Williams made too many mistakes in the zone with that fastball and below-average changeup in his few big-league innings. He has an above-average slider and that pitch, down and in, is his best weapon against lefties. The command is going to need to come here if Williams is going to be more than a fifth- or sixth-starter type of arm.”

Williams did well to surpass expectations. He held down a spot in the rotation for the majority of the season, making 25 starts in 31 total appearances. He relied mostly on a four-pitch mix that included a four-seamer (49.1%), sinker (22.4%), slider (16.2%), and changeup (10.1%). He finished the season with an ERA of 4.07, a FIP of 4.03, and 117 strikeouts. He played like a slightly above average starter and his 2.5 WAR was second to only Jordan Montgomery among rookie pitchers. While posting average strikeout and walk rates, his calling card was limiting hard contact, which resulted in a 0.84 HR/9, 10th best in the majors among pitchers with at least 120 IP.

He continued this success in 2018, his best season at the major league level, where he was again a reliable starter, pitching 170.2 innings in 31 starts and posting a 3.86 FIP and 2.7 WAR. He utilized his sinker a bit less in favor of his slider and changeup in 2018, although little changed in regard to his K%, BB%, and HR/9. His average exit velocity, hard hit rate, and barrel rate were all above or close to the 75th percentile, though he may have also had a bit of luck with his BABIP compared to his 2017 campaign. His BABIP against dropped .030 from the previous season suggesting some of his improvement in 2018 was luck-based.

Those first two seasons were a great success for Williams. He mostly lived up to Eric Longenhagen’s evaluation but was able to overachieve by striking the right balance in his pitch mix and by leveling up on his command to induce softer contact he had before. His ability to elicit weak contact had him knocking on the door of elite status in the hard hit categories.

Trevor Williams 2017-18
Stat Average MLB Rank Percentile
HR/9 0.81 5th 96th
EV 86.6 14th 89th
Hard Hit % 30.0 7th 94th
Barrel % 5.1 29th 77th
*Ranks and percentiles calculated based on pitchers who logged at least 200 innings total during the 2017 and ’18 seasons.

It seemed that heading into 2018, with two full seasons under his belt, he had a recipe for success that he could continue to build on. Things took a turn for the worse, however. A U-turn, in fact. His ability to fool hitters into making weak contact started to dissipate. During the 2019 and ’20 seasons, Williams averaged a 1.88 HR/9, more than double his HR/9 from the previous two seasons and his hard hit rate ballooned to 35.7%, leading to a combined FIP of 5.45 and WAR of just 0.6.

So what happened? One thing that jumps out looking at the data from the past few seasons is the effectiveness of Williams’ fastball and slider. During the 2017 and ’18 seasons, his fastball/slider combo combined for a cumulative 47.1 runs above average using FanGraphs’ pitch values. This same fastball/sinker combo netted him -4.9 runs above average over the 2019 and ’20 seasons. In a recent interview with Sahadev Sharma of The Athletic, Williams talked about an oblique strain he suffered early in the 2019 season that adversely affected his pitching mechanics. Since being acquired by the Cubs, a big priority has been fixing his arm slot and getting it back to where it was in 2018 prior to the injury.

The subpar mechanics may have also been exacerbated by an ill-advised change in Williams’ pitch mix. Starting in the 2018 season, he began to move away from his sinker in favor of his slider, presumably looking to miss more bats. According to Williams, the decision was his own choice after he looked at the data and saw that the sinker was ineffective. But an adverse effect of the switch was that it reduced his arsenal of pitches and, in turn, the effectiveness of his fastball, which had been his best pitch in earlier seasons.

While Williams wasn’t the lion tamer of exit velocity that he was in 2017 and ’18, he was still well above league average in that category in ’19 and ’20. His xwOBA allowed, the expected value assigned to a batted ball by Statcast, increased at an even greater rate than hitter’s exit velocities would suggest, meaning that hitters were also having an easier time barreling the ball against him. It didn’t help that he also had a little bad luck as the actual wOBA during this time was worse than expected. His usage of the slider in 2019 and ’20 is even more interesting when looking at batted ball statistics for that pitch on its own. Williams diligently worked on his slider, gradually improving its Whiff% from 25.8% in 2017 up to 39.8%. Despite its effectiveness at making hitters miss, their 2020 wOBA against his slider was .420 compared to an xwOBA of .308.

In the wake of all of this, Williams reported to camp and showed up with a resurgent fastball. Let it be known that it’s an extremely small sample and spring stats are to be taken with a grain of salt. Studies have suggested that success (or lack thereof) in spring has a positive, marginal correlation to performance in the regular season. With such a small sample, it’s not uncommon to see results like Kevin Newman’s this spring, where he slashed .606/.641/.788 (33 plate appearances) in the Grapefruit League; he’s begun his 2021 campaign with a .214/.214/.429 line. Nonetheless, the following results from Williams are encouraging.

2021 Spring Training
13.2 1.32 0.951 7.2 0.7 0.7
SOURCE: Baseball-Reference

It’s a good sign that over 13.2 innings, Williams yielded only one homer and one walk. Among his 11 strikeout victims: Mike Trout, Mookie Betts, and Matt Olson.

On Monday, Williams made his regular season Cubs debut and was very impressive. In fact, he retired the first 15 batters he faced and took a perfect game into the sixth inning before Omar Narváez broke it up with a single. While it’s just one game, it extends the small sample of spring success, now enhanced with some Statcast data. His pitch mix was almost evenly distributed across his five offerings. Notably, his fastball was used just 29% of the time, down from a career average of 49.5%, and his sinker usage was at 20% compared to last season’s 8.2%. He ended up leaving in the seventh after allowing the first two runners to reach base (they would eventually score) but it was solid night overall, with a line of 6 IP, 2 R, 2 H, 2 BB, and 6 K. The whole weak contact thing? For just this one start, on a total of 13 balls put in play, hitters had an average exit velocity of 86.3, which yielded just four hard hits. It was, dare I say, vintage Trevor Williams.

A strong result on Monday doesn’t mean Williams is back for good; it’s one start. But it certainly seems plausible that the Cubs and Williams might have figured things out. If he can keep it up throughout the season, the Cubs are getting quite a bargain.

Chet is a contributor for FanGraphs. Prior to FanGraphs, he wrote for Purple Row. When not writing about baseball, he is a data scientist and outdoor sport enthusiast. He can be found on Twitter at @cgutwein.

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Excellent analysis and welcome to FanGraphs.