The Brewers Should Consider Brad Keller to Shore Up Their Starting Rotation

Piecing together innings in the starting rotation has been among the chief challenges for Brewers personnel this season. Injuries to Wade Miley, DL Hall, and Jakob Junis ravaged the team’s depth early on.

The club was making it work by plugging Bryse Wilson, Robert Gasser, and Tobias Myers into its rotation, testing the limits of the production it could receive from its on-hand starters without external reinforcements. After Joe Ross hit the injured list with a back strain on Tuesday, however, the Brewers have crossed into the territory of needing to add an outside starter.

Enter Brad Keller.

The Chicago White Sox designated the right-hander for assignment on Sunday, concluding a 16 2/3-inning stint on the South Side. Before signing a minor-league deal there in March, Keller spent the first six years of his career as a Kansas City Royal, meaning all his big-league experience has been on teams with lackluster track records at pitching development.

It is not surprising, then, that Keller’s recent résumé is similarly poor. Since the start of the 2021 season, he owns a 5.13 ERA, 4.88 FIP, and 4.96 SIERA. Times got especially tough in an injury-plagued 2023, but Keller has not been effective when he has been healthy enough to pitch.

Despite those inauspicious results, the foundation of a serviceable back-of-the-rotation arm is there. So is the fit with this Brewers team.

Keller’s greatest attribute is one that would play well with the Brewers’ infield defense behind him. He boasts a 51.8% ground ball rate for his career, and that has held at a near-identical 51.4% since his struggles began in 2021.

In that latter span, Keller has yielded a .267 batting average on ground balls. That’s the 10th-worst among pitchers with at least 300 innings pitched, and it’s well above both the league average of .234 and Keller’s expected batting average on grounders of .220. Of the 115 pitchers on that leaderboard, he has the second-highest gap between his actual and expected batting average on ground balls.

A good deal of that misfortune can be attributed to the defenders behind him. According to Statcast, infielders behind Keller have combined for -8 outs above average since 2021, the 23rd-worst mark in baseball. Meanwhile, the Brewers’ infield ranks sixth in baseball with 25 outs above average. The change of scenery could provide an immediate boost to Keller’s results.

Beyond his penchant for inducing ground balls, Keller has always had an intriguing arsenal. It seems he is settling on the best way to shape and deploy it.

Keller has thrown at least five distinct types of pitches throughout his career but has leaned predominantly on a three-pitch mix this year. Between Triple-A and the big leagues, 93.4% of his pitches have been a cutting fastball, a slider, or a changeup. His sinker and the curveball he developed in 2023 have subsided into occasional change-of-pace pitches.

Statcast classifies Keller’s primary fastball as a four-seamer, but most of them have a few inches of glove-side cut. After doubling the lateral movement on his slider from 2022 to 2023, he has fashioned it into more of a slurve-like pitch this year, possibly to create greater separation from the cutter.

Developing the changeup is perhaps the greatest stride Keller has made. Over the last two years, he has added more vertical drop to the pitch and ramped up its usage to positive results against both lefties and righties.

Keller has always been a pitch-to-contact specialist, but his refined pitch mix appears to be generating more swings and misses. In 30 ⅔ professional innings this year, his whiff and swinging strike rates are up to 27.8% and 12.1%, respectively. Hitters have made contact on 78.2% of swings on pitches in the strike zone, including 81.6% in the big leagues. That’s a noticeable drop from Keller’s career 87.7% zone contact rate entering 2024.

This is a pitcher who can be serviceable as a member of Milwaukee’s run-prevention unit. Just as importantly, he is stretched out and can cover some innings while other starters are sidelined. As of this writing, Keller is available on the waiver wire. If the Brewers have an opportunity to claim him, they should consider doing so.