Mound Visit: How Cahill, Pirates have changed their pitching approach

BRADENTON, Fla. -- Back in 2015, fresh off a 98 win season, the Pirates went into the offseason knowing they needed starting pitching help. A.J. Burnett was retiring, J.A. Happ was probably leaving, and while Jameson Taillon and Tyler Glasnow would be ready for the majors midseason, they needed some depth to bridge the gap to then.

Yeah, there are a lot of ex-Pirates to take in there. I’ll give you a minute.

One of the pitchers they pursued that winter was Trevor Cahill, but the right-hander eventually decided to head back to the Cubs for the 2016 season. The next offseason rolled around, the Pirates made another push for Cahill, and once again he turned them down. Then the 2018 winter meetings and the Pirates once again expressed interest in the right-hander. Once again, nothing happened.

So what Ben Cherington really did this week was kill this weird, admittedly kind of funny running joke that the Pirates always wanted this swingman pitcher, but could never get him. Well, the fourth or fifth time’s a charm.

“It just seemed like they really wanted me,” Cahill said Sunday. “It seemed like a good fit.”

To be upfront about Cahill, he isn’t going to be a revelation. Pitchers who sign on March 12 for $1.5 million aren’t going to turn a rotation around. At best, he’s a fifth or sixth starter. At worst, he’ll eat innings and take some extra workload off the Pirates’ young pitchers. The Pirates are going to need a couple guys like that to get through the season.

But it is interesting to see how Cahill has evolved as a pitcher since that first time the Pirates tried signing him five years ago to now. It’s very similar to how the Pirates’ pitching philosophies have evolved, too.

For most of his career, Cahill was a sinkerballer who got ground balls. When that was the trendy, popular thing to do across baseball, he was pretty good. He averaged just under 200 innings pitched a year and a 3.87 ERA over the first four seasons of his career, which included an All-Star nod and a little down ballot Cy Young consideration in 2010. But things started to go south in 2013, missing part of the year with an injury. He followed that with a horrible 2014 campaign that included him being sent down to the minors to work on his mechanical problems. After bouncing around in 2015, he finally found some success with the Cubs later that year.

This is where Cahill’s career gets weird. He excelled with the Cubs in 2016, posting a 2.74 ERA in a bullpen role. He went back to the rotation in 2017 and got hit hard. In 2018, he got another look as a starter with the Athletics and recorded a 110 ERA+ over 110 innings. He then went to the Angels and pitched so poorly that he lost his spot in a mediocre rotation. He signed a minor league deal with the Giants before the 2020 season, and while he didn’t make the opening day team, he eventually pitched to a 3.24 ERA over 25 innings.

So Cahill has basically alternated between having a good year or a bad year for the past six or so years. Perhaps not the best omen for 2021, but of course that means nothing for the future.

But between those highs and lows over the last six years, we’ve seen Cahill slowly trending in the same direction: Less sinkers, more curveballs and changeups:

For the first time in his career, Cahill didn’t go to his sinker the most out of his five-pitch mix. Granted, he also has a four-seamer to work with and his slider has evolved into more of a cutter, so he has options with his fastball. Still, at his core, he’s a sinkerballer. The other two fastballs are just different looks.

His sinker has always been hit hard. The changeup and curve have been a lot harder to barrel up. His curveball was particularly devastating in 2020, with batters going 0-for-21 against it. It’s a high spin pitch, getting nearly 3,000 RPM, and has good vertical and horizontal movement. His changeup had 8.4 more inches of vertical movement than the league average changeup, going by Baseball Savant’s measurements. Honestly, it’s probably his better sinking pitch nowadays.

Cahill has slowly been using those two pitches more and more each year while decreasing his sinker usage. It’s why he posted much better results last year, even as his sinker was hit harder than it ever had been before:

“I think it's just survival,” Cahill said on the reason for the change in his pitch mix. “You try something out, you watch games and you struggle with somebody. I remember guys where I'm like, 'I can never get these guys out,' and then they're like, 'Try throwing them all curveballs.' And it was like, 'Oh, that makes it a lot easier.' So it's just figuring it out, what works, and always adjusting.”

Cahill is a journeyman pitcher who has spent as much time in the bullpen as a rotation over the last five years. He needed to adapt in order to stay in the league, and he has slowly been doing that. So much so that he isn’t really a ground ball pitcher anymore. 

Yes, 25 innings in a 60-game season just screams “small sample size,” but for someone who had averaged a roughly 55% ground ball rate for the first 11 years of his career, dropping down to 33.3% is drastic. And in his 11 year career, he never had an 11 game stretch where he had a lower ground ball rate than he did last year:

Cahill replaced those groundouts with strikeouts, and did so at a pretty impressive clip, fanning 29.2% of his batters faced. Again, it could be the product of the small sample size, but he gets really good movement on his secondary pitches and he throws them just about as often as the fastball anymore. He has the stuff to get whiffs.

All of this fits Oscar Marin and the new Pirates' regime's philosophies like a glove. Gone are the days about having to throw a sinker because everyone throws a sinker. Pitch to your strengths. We could hypothesize that if Cahill would have signed with the Pirates in 2016, he probably would have thrown his sinker more. That probably wouldn't have worked.

In all reality, the Pirates are probably just going to be another stop in Cahill’s recent globetrotting. He has a couple good pitches and could be a decent junkballer at the backend of a rotation. If things go particularly well, perhaps the Pirates can flip him for a prospect at the deadline.

But the real takeaway is that this isn’t the same Cahill the Pirates tried to sign five years ago. Cahill isn’t joining the same Pirates team he passed on five years ago, either. They’ve both evolved since then. Is it a match made in baseball heaven? No, but there’s obvious appeal for both, which is why the Pirates finally got their guy, albeit a slightly different, and presumably better, version of him.