From DFA’d to premier setup man in less than four years, Brock Stewart has one of the best stories in baseball and is poised to play a big role on the 2024 Twins. 

In 2019, Stewart was DFA’d by the Dodgers before being picked up by the Blue Jays. Stewart only threw 21 innings with the Blue Jays but his time there was the worst of his career. He pitched to a 55 ERA+ along with a career low in K/9 at 6.6. Furthermore, his fastball sat at a middling 91 MPH. As a result, he was once again DFA’d. After a lost season in 2020 due to covid, Stewart looked to get back on the mound but was hit by a slew of elbow injuries and was sidelined for a year. Now as a 30 year old, he was running out of options to be able to keep pitching and he turned to Tread Athletics to give him another shot.

Tread is a sports performance center located in North Carolina that specializes in using advanced data to highlight weaknesses and improve all aspects of a pitcher's game. While at Tread, Stewart focused on two things: change his slider to a sweeper and add a cutter to his repertoire. Within months of working at Tread, he hit a new best of 96 MPH on his fastball.

Stewart was eventually signed to a minor league deal with the Twins after seeing his new pitch mix and mechanics he developed while at Tread. On April 27th 2023, Stewart made his Twins debut pitching two scoreless against the Royals. Stewart pitched only 27 innings in 2023 but they were dominant. He allowed only 2 earned runs and had a .65 ERA while striking out 12.7/9.

When looking even deeper into some of his pitches, you can truly see his effectiveness. He throws his fastball the most out of any of his pitches at 39% and for good reason. Compared to his pre-Tread fastball, the average MPH has bumped over 6 MPH to 97.3. He is able to generate a high spin rate of 2600 which gives him a well above average Bauer Unit score of 26.76 (league average is 24). On top of his high spin rate, the spin efficiency is great as well at 82%. For comparison, an average MLB 2-seamer has a 2150 spin rate and a spin efficiency in the range of 75-100%. This means that Stewart has the spin profile of a 2-seamer with the spin rate of an electric 4-seamer. The result of this is a xwhiff+ score of 132, above the likes of dominant pitchers such as Spencer Strider and Alexis Diaz.

The biggest focus during his time at Tread was the development of a new sweeper and it transformed his pitch mix. Prior to his injuries, Stewart was throwing a more traditional gyro slider which only generated 4.7 inches of horizontal movement. His sweeper that he showed off in 2023 has a whopping 15.6. Compared to his 2018 slider, the opponent’s xBA and hard hit% dropped off substantially when facing this sweeper. This pitch was developed as a more effective way to get righty batters out and it did just that. He threw the sweeper to righties 71% of the time and had a stuff+ score of 132 when facing same handed hitters.

The final of his three main pitches is the cutter, another pitch he developed at tread. The cutter acts as a medium between the fastball and sweeper at an average of 93.3 MPH and 2.3 inches of horizontal movement but it is just as effective. Opponents batted a mere .071 against it and he had his highest put away% of 40% while using the cutter. Even the expected stats back up the dominance of the pitch with a xSLG of only .231.

When looking at the 2024 Twins outlook, the bullpen is slated to be the biggest bright spot of the team and a full season of Brock Stewart is massive to the success of the pen overall. It may be easy to write off his 2023 season as something like a fluke due to the low innings count but all underlying numbers and pitch data suggest otherwise. 

Finally, Stewart’s story shows the increasing prevalence and usefulness of advanced data and pitch tracking. Sports centers such as Tread and Driveline are becoming increasingly popular as it allows athletes to use data they normally wouldn’t be able to see to fully tap into their abilities. It also gives MLB teams further insight and aids them in making potentially multi-million dollar deals. Without them, the Twins would have never signed Brock Stewart who looks to be one of the biggest factors of a Twins team that is poised to run it back in the playoffs.