Pirates Sign Trevor Cahill for Added Depth

With nearly half of spring training already over, the Pirates made a last-minute addition to their starting rotation last week, signing Trevor Cahill to a one-year, $1.5 million contract with an additional $1 million in potential incentives. Cahill becomes the second veteran arm Pittsburgh has added this offseason, joining his former teammate from the Giants, Tyler Anderson. In a season where every pitching staff will be stretched thin, both ex-Giants give the Pirates much needed rotation depth.

Cahill joins an extremely young Pirates roster. Depending on what happens with Todd Frazier, who is in camp as a non-roster invitee, Cahill could enter the season as the oldest member of the 26-man roster. Pittsburgh was very aggressive in moving whatever value they could find from their starting rotation this offseason. Joe Musgrove and Jameson Taillon were both traded away within a week of each other, and Trevor Williams and Chris Archer both left in free agency. Steven Brault and Chad Kuhl have the most seniority now with nine seasons and 5.6 total WAR between them. Mitch Keller will get another chance to translate his excellent minor league track record and prospect helium into actual production at the major league level. Because of either their advanced service time or pedigree, those three should have rotation spots locked up with Anderson slotting into the fourth slot. That leaves Cahill and JT Brubaker to round out the staff — assuming the Pirates use a six-man rotation.

Pirates GM Ben Cherington has said that’s how he’d like to approach the season:

“We like the idea of having six starters on the team. Whether we’re actually using all six starters or are using them to come in behind guys and provide length or back and forth, we’ll see how that plays out. We just wanted to add as much starting depth as we could after the offseason moves.”

We’ve seen plenty of other teams add pitching depth this offseason in an effort to protect their pitchers from taking on too big of a workload after the shortened season. Cahill is a good fit for a team like the Pirates, which will need pitchers to soak up innings, and he has experience in both the rotation and the bullpen.

Manager Derek Shelton has indicated that he prefers to use a five-man rotation and evaluate the workload of his staff from there. If the Pirates end up shifting to a shorter rotation for whatever reason, adding Cahill might have pushed out the most interesting starter on the roster in Brubaker.

After a solid debut in 2020, ZiPS projects Brubaker to be Pittsburgh’s best starter this year. He does enough things well enough, and has two excellent breaking balls as a foundation to build off of, to provide some quality innings for the Pirates. If only five pitchers are going to be selected for the Opening Day roster, Brubaker could find himself relegated to the alternate site to start the year. Considering the spotty health history of Brault, Kuhl, and Cahill, and the workload management that will inevitably come, there will be opportunities for Brubaker to get his innings in. And if things break right for Cahill and Anderson, they’re likely mid-season trade candidates as well. Brubaker will get his shot to prove he can stick in the majors eventually.

In San Francisco, Cahill split his time between the rotation and the bullpen, making six starts in August and early September and then shifting to relief work to finish the season. In all, he compiled just 25 innings last season but they were a nice bounce back after a rough stint with the Angels in 2019. After his strikeout rate dropped to 17.8% in Los Angeles, he got it up to 29.2% with the Giants, a career high for him.

That jump in strikeout rate is the result of a changing pitch mix. Cahill has always relied on his sinker as his primary pitch, and while it’s helped him generate a ton of contact on the ground, it hasn’t been a very effective pitch outside of that single feature. He’s steadily decreased his sinker usage each year since 2016, and in 2020 it made up a career-low 24.6% of his pitches. Instead, he turned to his changeup far more often, with little bumps in usage for his four-seam fastball and curveball too. Those three pitches formed a deadly trio for him. Each of them possessed a whiff rate of at least 32.3% and an xwOBA on contact no higher than .343. His curveball, the pitch that helped him revitalize his career back in 2017, ran a 43.8% whiff rate, the best mark he’s posted with the pitch since 2016.

Adjusting his pitch mix to feature his three best pitches definitely helped him raise his strikeout rate, but it had some unfortunate side effects. Since his debut in 2009, Cahill has run a groundball rate around 54% and his sinker was a major reason why. But with the use of his sinker steadily dropping each year, his groundball rate has also declined. Last year, his groundball rate fell below league average for the first time in his career, all the way down to 33.3%. All that extra elevated contact didn’t translate into a home run problem. In fact, because opposing batters have such a hard time squaring up his curveball and changeup, his home run rate fell from 22.5% to 12.5% even though the rate of barrels he allowed rose to 10.2%.

Even more worrisome was a walk rate that spiked to 13.2%. With so many more secondary pitches making up his repertoire, he had trouble locating in the zone as often. When he did pitch in the zone, opposing batters swung less often, likely because they weren’t being fed a steady diet of sinkers anymore. Still, he threw his changeup and curveball in the zone just 40% of the time, and he didn’t see a discernible change in his chase rate. He managed to work around all those additional free passes with his fantastic strikeout rate and extremely low BABIP.

Even though he signed with just over two weeks until Opening Day, and he still has to pass through intake procedures, the Pirates expect Cahill will be ready for the beginning of the season. He was throwing up to 60 pitches in simulated games before he signed and shouldn’t take long to ramp up his workload from there. Beyond the minor nits to pick with the effect his status on the roster has on Brubaker, Cahill should give the Pirates some much needed depth in their rotation.