The bullpen used to be a place where failed starters would go to kickstart their career or provide a path for a bounce-back. Mariano Rivera started 10 games for the Yankees in his rookie season. John Smoltz and Derek Lowe had strong seasons as starting pitchers before late-career moves to the bullpen. Edwin Diaz was a starting pitching prospect for three years in the Mariners' organization before they moved him to the bullpen in Double-A in 2016, and Mason Miller was a talented but oft-injured starting pitcher until the Athletics made him a full-time reliever in 2024.

However, the Miller move is a path that's becoming more common for young starting pitchers, like Hunter Brown, Garrett Crochet, or Joey Cantillo.

So far, Miller has stayed in the bullpen, unlike the three names I just alluded to, but when the Athletics initially moved him to the bullpen, it was to find a way for him to help their big league team more immediately. It just turned out that he was so dominant out of the bullpen that the team decided to keep him there. Garrett Crochet was similarly dominant out of the bullpen for the White Sox in 2021 and 2023, but he always viewed himself as a starter and is now an ace for the Red Sox.

Using the bullpen as a training ground for young starting pitchers is becoming more common because of the way a bullpen role forces a pitcher to simplify his approach. When I talked to Reid Detmers earlier this month about his move to the bullpen, he stressed that there was no time to mess around in the bullpen: "It's more of just attacking with my stuff. As a starter, you kind of work around guys, like you're trying to hit the corners and stuff. Where, in the bullpen, you need to attack."

Dodgers reliever Ben Casparius, who also spent his minor league career as a starter, told me something similar back in May: “I think the relief side of things has helped with some of my starts too, in just focusing on one pitch at a time and not projecting or looking ahead towards the next inning. It’s just gotten me into a mindset of, every inning, here’s my best stuff."

That's a similar mindset that Cleveland Guardians starting pitcher Joey Cantillo adopted this season after pitching his first 28.1 innings out of the bullpen.

"I think the biggest thing that I kind of put upon myself is like, 'Hey, you don't have time to settle in,'" he told me during a series against the Mets last week. "When you're coming out of the bullpen, you could be in the fifth inning, could be the fourth inning, could be the eighth inning. You don't know how many pitches you have. There's a sense of urgency from pitch one, like, 'Hey, let's get ahead; value each pitch.'"

Last year in the minor leagues, Cantillo posted a 15% walk rate, which was 6.13 BB/9 innings. This year, his walk rate dropped to 11.9% in his MLB innings but just 8.76% in his limited minor league sample size when he was moved into the starting rotation. While his new attack-centric mindset isn't transitioning to substantial gains in his walk rate and command stats right away, it is now a fixture in his mental approach when he's on the mound.

"I didn't do a great job of throwing strikes [earlier in the season]," he admitted. "It's kind of why I always say, everyone knows it, but this game is simple when you're getting ahead of guys and you're throwing strikes." His new attack mindset is slowly beginning to help with that.

"It's something I'm trying to bring to starting. You know, the start the other day [August 3rd against the Twins], I had a tough first inning, four hits to start the game, but I attacked in the zone to start the game and had a sense of urgency. You don't know how many pitches you're gonna have, even though it's a start, so let's attack from the beginning. Kind of bringing that mindset into it. But, at the end of the day, it's still baseball. You're still just trying to get outs."

While one of the components of getting those outs for Cantillo has been his new mindset, another has been a slight change in his approach.

"I've thrown a little less fastballs, and I'm trying to use my curveball more," he explained. "When they sent me down [to Triple-A in May], they stressed to throw that curveball more." As you can see from Alex Chamberlain's Pitch Leaderboard below, Cantillo has indeed started using his curveball more as a starter.

Alex Chamberlain Pitch Leaderboard

On the season, it's an above-average pitch by stuff and command. The pitch is 76.6 mph with 21 inches of vertical break and nearly nine inches of glove-side movement. That's the 96th percentile in baseball in terms of total break. However, he also has a well-above-average zone rate and an above-average strike rate on the pitch, which has led to a solid 34% CSW. Overall, the pitch doesn't miss many bats, but much of that has to do with its performance against righties. It actually grades out as his best pitch by Pitcher List's PLV grade.

Pitcher List

Against righties, Cantillo has just a 6.3% swinging strike rate (SwStr%) on his curve, and his command of the pitch is worse. Those numbers have been slightly better since Cantillo came back up as a starting pitcher, but much of that is likely due to sequencing. His usage in specific counts and location has not changed much, but he's keeping the curve away a little more often and using it in two-strike counts slightly more often to righties. Even in Cantillo's mind, the benefit of the curveball is more about keeping hitters guessing than anything.

"I need to have good fastball execution, good fastball command in the zone, and then throw that curveball to both sides of the plate," he explained. "When I'm landing that in the strike zone, I think it just gives hitters something else to have to think about before they see a fastball or change-up."

Against righties and lefties, the curve is his third most-used pitch. He has thrown it 25% of the time to righties as a starter, but he will primarily rely on his four-seam fastball and change-up, and he has used the curve just 18% of the time to lefties as a starter since he also mixes in a slider 17% of the time. "Out of the bullpen, I think there were times I didn't really throw the slider," recalled Cantillo. "Now that I'm pitching deeper into games, I'm gonna see a few more lefties, so I gotta start throwing that slider. You gotta put in the hitter's mind a little bit like, 'Hey, this guy throws this pitch a little bit' and establish that."

Perhaps that limited usage is what's making the slider impactful, but in his seven starts, the pitch has a 17% SwStr% against lefties, while not allowing a single hard-hit ball and producing just a .200 average and a .350 xwOBA. But it's a slower slider at 84 mph, so perhaps it plays well off the curveball to create some deception to lefties.

But both the slider and curve are complementary pieces to Cantillo's two main offerings: a four-seam fastball that he gets elite extension on and a dominant changeup.

While Cantillo is known more for his changeup, his fastball is his most-used pitch and is a unique offering since it has 7.4 feet of extension, which is among the most of any starter in baseball. Extension measures how far out in front, or how close to home, a pitcher releases the ball, with the MLB average being 6.5 feet. So, on average, Cantillo releases his fastball a foot closer to home plate than most pitchers, which means the pitch gets on a hitter faster and makes his 91.5 mph fastball seem closer to 93-94 mph.

Pitcher List

"I did a lot of Tom House when I was young, and a lot of that stuff was kind of about getting your hand far out there," recalled Cantillo. "Stride length was also really what we stressed when we were younger. Now, [extension] is not something I think about. It's just kind of how I throw. The extension plays, but that's not something I've ever really thought about or trained for. I'm thankful I have it, obviously."

Yet for Cantillo, the bigger focus with his four-seam fastball is getting back some of the velocity that he's lost this season: "I'm not quite throwing as hard as I used to, and I'm working on that stuff. It's little adjustments we're making day by day. I think for me, it's, can we continue to see that fastball get back up to where I know it can be back into the mid-90s and throwing it in the zone."

Again, Cantillo is stressing the need to attack the zone with his pitches. It's something he's even focusing on with his best pitch, his change-up.

Overall, on the season, the pitch has a 24.3% swinging strike rate, so you'd think a pitch that gets that many swings and misses is causing hitters to chase off the plate consistently. Yet, Cantillo has just a 31% chase rate on his changeup, which is 39th percentile in baseball. Part of his success on the pitch this season has been that he's actually throwing it in the strike zone more often and using it earlier in counts than he did last year.

"I think recently, the way it's played, and this was something that was told to me when I first came up last year, is eliminating the change-ups that are really down under the zone," Cantillo said. "I think it plays best in the zone. It's not like a super depthy pitch. Yes, it goes down, but the change of speed is what helps it play well. So really, I just trying to be aggressive with it and throw it in the strike zone."

When Cantillo says his changeup isn't super depthy, he's referring to the fact that the pitch gets only 14.7 inches of total break. That's below league average. His changeup drops only 33 inches, when you factor in gravity, which is almost an inch less than the normal changeup. He also gets over an inch less horizontal movement than comparable changeups, so the pitch tends to not grade out well in most pitch models.

Pitcher List

However, as Cantillo said, the key to his changeup is the velocity gap between that and his four-seam fastball and the way the two pitches tunnel out of his hand, so hitters can't tell the difference until it's too late. This is also where his elite extension comes into play because a hitter has less time to differentiate between those two pitches.

So if the pitch doesn't rely on depth or movement for success, then he doesn't need to get chases out of the zone. That's why he's thrown the pitch in the strike zone 44% of the time in his seven starts, with 59% of his changeups being low in the strike zone and 36% being over the middle of the plate rather than on the inside or outside corner. When he was coming out of the bullpen, Cantillo had just a 38% zone rate on his changeup and was throwing it low in the zone 50% of the time, so the pitch is landing in the lower part of the strike zone more often, and a lot of that has to do with how he picks up his target and where he aims at release.

"For the most part, I'm trying to keep it simple and be pretty middle with [the changeup," Cantillo explained. "If I'm way ahead in the count, that's probably where I'll shift my sights down, but I think when I'm having the most success, it's very aggressive. No matter what the count is, I'm throwing it through the heart of the plate, through the catcher, and letting the action take it to where it is, but kind of stressing more contact with the pitch."

Part of the reason that Cantillo is able to succeed with a more contact-focused approach to his changeup is that he uses a unique "Vulcan" grip on it. The Vulcan change is named after the Vulcan symbol on Star Trek, where the ring finger and pinky finger are split together on one side, forming a "V" with the middle finger and pointer finger on the other side. The baseball is then jammed down into that "V" to create almost a split-finger change-up.

"My high school coach taught it to me, but I didn't have to throw it that much in high school, and I didn't know where it was going at all," smiled Cantillo. "Then, when I got drafted by the Padres, our throwing program was, like, 'You're gonna throw change-ups. No matter how far you throw, you're gonna throw change-ups every day at 90 feet.' The first couple of months of rookie ball, I'd throw it, and I had no idea where it was going. You're splitting it deep in your fingers, so the feel for it took a little bit, but I think it's like anything else. You start throwing it as hard as you can, and you get a feel for throwing it and making an adjustment. That's kind of a day-by-day thing. There are days when I gotta raise the sights, and there are days when I gotta lower the sights."

But Cantillo's time in the bullpen taught him how to attack with his changeup more effectively and efficiently than he had before, and it has led to success on that pitch that he's never had before. It also creates a potential building block for the 25-year-old and the Guardians to build off of.

"Honestly, I think [my goal for the final two months is] just continuing to get better," he stated last week. "There's been some inconsistencies, and I think, like everybody else here, I want to be as consistent as possible. That's what makes a good big leaguer."

Part of that consistency for Cantillo has come from a more solidified role. With Luis L. Ortiz on paid administrative leave following an investigation into illegal gambling and Shane Bieber traded to the Blue Jays at the trade deadline this year, there isn't much competition for Cantillo's spot in the rotation. He's getting the ball every five days for a Guardians team that has the third-best record in baseball over the last 30 days. Cleveland is now in possession of one of the final playoff spots in the American League, and the team has won four of the last six starts that Cantillo has made.

"Honestly, up here, it's, it's a good day if you win the baseball game," he declared. "You know, I contribute to the team once every five days. It's do your job, pitch deep into the game, give the team a chance to win. I think if I'm consistent, and in the process, I'm filling up the strike zone, being aggressive with the change-up, good things are going to happen."

With his next five starts projected to come against the Braves, Diamondbacks, Rays, Red Sox, and Rays, good things could also happen for fantasy managers who roster Cantillo for the remainder of the season.