Phillies closer Jhoan Duran returned from the injured list last week, a move that made their bullpen complete. Because of injuries to Orion Kerkering, Jonathan Bowlan and Duran, the team had their full complement of high-end relievers for only six of the first 35 games this season.
For an off-season mired in “running it back” talk, the Phillies position group that underwent the largest face lift was the relief corp. Philly had made minor tweaks to its bullpen in past off-seasons, but it seemed an overhaul was required after the group finished No. 20 in both ERA (4.27) and FanGraphs Wins Above Replacement (2.9) in the majors in 2025.
They had a problem with the long ball, which was a big reason the bullpen revamp was inevitable. Despite the lightest workload in MLB a season ago, Phillies relievers surrendered 74 home runs - good for 15th most in the majors.
In an exclusive interview, I asked Phillies pitching coach, Caleb Cotham, if that was something he and the organization zoned in on addressing in the off-season. “You just want good pitchers,” Cotham told me, denying a direct correlation. But he did give me an idea of how they look to build a staff. “You kind of want guys that don't walk guys, strike guys out and give up ground balls - not fly balls - because ground balls are never home runs.”
Philadelphia's pen also had the fourth-lowest ground-ball rate last year, making the club unable to rely on rolling grounders for easy outs or double plays. Unsurprisingly, Philly relievers were dead last in baseball at generating double plays.
Those numbers are glaring for a team with World Series aspirations - you need to be sure your relievers can shut the door, not put you at risk. “[It’s] not that necessarily you're anti-fly ball, but the risk with fly ball is home runs. So if we had one play [to make] in a playoff game, I'd play a ground ball [guy] every day. But I’d pick that after a strikeout, and I’d pick that after not walking someone.”
That’s the order he provided and the organization prefers:
“You need relievers to miss bats in big spots because balls in play fall for hits,” the pitching coach explained. This season the team has felt that more than any other club in the majors. The Phillies pitching staff has allowed the highest batting average on balls in play - 25 points higher than the next worst team.
However, there’s more to it than just the result. “You have to look at the makeup of each guy,” he said. Cotham explained that his preferred results order works in conjunction with how the guy handles big moments, and you look at the results only when you do not know the makeup of the guy and how he reacts in pressure. This ties in to wanting good pitchers.
Those things must go hand-in-hand - the attitude of the player on the mound, plus the type of contact they allow. Matt Strahm, the veteran leader of the bullpen last season, is a perfect example. He was one of the most effective pitchers in baseball who handled big moments repeatedly for the club during his tenure in Philly, but his fly ball rate had increased year over year. While he limited home runs during the regular season in 2025, that trend came back to haunt him when he gave up the go-ahead home run to Teoscar Hernández in Game 1 of the NLDS. He is no longer with the club.
Whether Cotham and the front office had it at the forefront of their minds when making roster decisions or not, there is a startling difference between the top three relievers coming in versus those going out when it comes to hit type a season ago.
The three newcomers had a groundball rate nearly double the rate of the three pitchers they’re replacing.And their flyball rate? Cut the former Phillies’ rate in half (36% to 18%) and you get the rate of the players replacing them on the payroll.
Cotham is well-known for his ability to bring out the best in the Phillies staff, but his role goes far beyond getting handed a 13 man pitching staff and being told to do his best with what he is presented. He has a hands-on part in identifying potential arms to join the roster, working closely with the “really good minds” in the scouting department and front office.
Sometimes, those conversations may be as simple as “‘here's what I see and why it might not show up like [advanced tools and metrics show] yet,’ or ’hey, I think we're light on this, we're maybe heavy on that.’
Other times, there is a specific focus on addressing areas of need and knowing what they can deliver on. “You're piecing all those pieces together and trying to take that and go - ‘what do we know we have? How do we like to use the pen? Do we have solutions for all the different types of hitters - lefty, righty, up, down, spin, split?,’” Cotham detailed. “Just trying to put guys in the best spots to have the most success, but also having enough variety in the pen. There's unique looks, there's different slots.”
Cotham also feels they know what they are best at as a unit and that helps when deciding between multiple options. “I think we have a good sense of what we can and can't help quickly. Like effect change and intervention, so some things are harder than others,” the pitching coach explained honestly.
Tim Mayza, for example, was originally a waiver claim for depth late last season. This year, he made the Opening Day roster as a fourth lefty in the pen because of his improved slider - something Cotham’s group worked on with him quickly. “Cotham and the pitching group in general has done a great job of communicating, helping me try some new grips, try some new thought processes," Mayza explained to our Alec Kostival earlier this season. “Once we got to Spring Training, we kinda hit the ground running with the slider, in particular."
The look or angle from Mayza is not as drastic as Kyle Backhus, a left-hander who throws completely side-armed - something the Phillies have not had in a long time. Keller and Bowlan both have deep repertoires as former starters, allowing them to throw different looks and patterns to hitters on either side.
Besides inducing grounders, their fastballs were also elite last year, with Bowlan generating more swing-and-miss on the fastball than any other reliever in 2025 that threw 200+ heaters. Duran - well it is rare to see someone who can throw that hard while forcing that many ground balls.
Add all of this up, and you can see the staff, front office, and scouts weren’t just “running it back” when they made changes to the pen. They restructured a struggling unit, changing it from a growing problem to a clear strength.
