Brock Stewart, who went from being a DFA to becoming a premier setup man in less than four years, has one of the best stories in baseball and is poised to play a big role with the Twins in 2024.
In 2019, Stewart was DFAed by the Dodgers and later acquired by the Blue Jays. Stewart pitched just 21 innings for the Blue Jays, but his time there was the worst of his career. He posted an ERA over .55 and a career-low K/9 of 6.6. Additionally, his fastball was stuck at a mid-range velocity of 91 mph. As a result, he became DFA again. After missing the season due to the coronavirus in 2020, Stewart attempted to return to the mound, but a series of elbow injuries kept him sidelined for a year. Now 30 years old, he was running out of options to continue pitching and turned to the Tread Athletics for another chance.
Tread is a sports performance center located in North Carolina that specializes in using advanced data to uncover pitchers’ weaknesses and improve every aspect of their game. While at Tread, Stewart focused on his two things. Two things to do are change the slider to a sweeper and add a cutter to your repertoire. Within months of starting at Tread, he set a new fastball record of 96 miles per hour.
Stewart ultimately signed a minor league contract with the Twins after seeing the new pitching mix and mechanics he developed during his time with the Treads. On April 27, 2023, Stewart made his Twins debut with two scoreless innings against the Royals. Stewart pitched only 27 innings in 2023, but had a dominant pitching performance. He only allowed 2 earned runs, had a .65 ERA, and 12.7/9 strikeouts.
A deeper look at some of his suggestions will truly demonstrate his effectiveness. He throws his fastball the fastest of all his pitches at 39%, and there’s a good reason for that. Compared to his pre-tread fastball, his average MPH has increased by over 6 MPH to 97.3. He is able to generate a high spin rate of his 2600, well above the Bauer unit average score of his 26.76 (league average is his 24). In addition to the high spin rate, the spin efficiency is also impressive at 82%. For comparison, his average MLB two-seamer spin rate is 2150, with spin efficiency in the 75-100% range. This means Stewart has a two-seamer spin profile with the spin speed of an electric four-seamer. As a result, he had a whiff+ score of 132, which was higher than such strong pitchers as Spencer Strider and Alexis Diaz.
His biggest focus during his time at Tread was developing a new sweeper, which changed his pitch mix. Before his injury, Stewart was throwing a more traditional gyro slider with only 4.7 inches of horizontal travel. The sweeper’s batting average in 2023 was a whopping 15.6. Compared to his slider in 2018, his xBA and hard hit rate for opponents decreased significantly when playing against this sweeper. This pitch was developed as a more effective way to strike out right-handed batters, and it did just that. He threw sweepers to right-handed batters 71% of the time, and his Stuff+ score when facing the same batters was 132.
The last of his three main pitches is the cutter, another pitch he developed in the tread. The cutter averages 93.3 mph and has 2.3 inches of horizontal movement, acting as a medium between the fastball and the sweeper, but is just as effective. Opponents batted just .071, and he posted his highest put-away percentage of 40% while using a cutter. The expected stats also support the pitch’s dominance with an xSLG of just .231.
Looking at the Twins’ outlook for 2024, the bullpen is slated to be the team’s biggest bright spot, and a full season for Brock Stewart will greatly impact the overall success of the pen. While it might be easy to dismiss his 2023 season as a fluke due to the lack of innings, all the underlying numbers and pitching data suggest otherwise.
Finally, Stewart’s story illustrates the growing prevalence and usefulness of advanced data and pitch tracking. Sports centers like Tread and Driveline are becoming increasingly popular because they allow athletes to maximize their abilities using data they wouldn’t normally see. It also gives MLB teams additional insight and helps them make potentially multi-million dollar deals. Without them, the Twins wouldn’t have signed Brock Stewart, who appears to be one of the biggest pieces of a Twins team poised to make an upset in the playoffs.
