PHILADELPHIA — A few minutes after he threw a pitch at 100 mph — legit triple digits, not the rounded-up stuff — Jonathan Bowlan was in the dugout inspecting an iPad. That is when he saw it for the first time: 100.2. He found Phillies pitching coach Caleb Cotham nearby on Monday night.“Hey, Caleb,” Bowlan said, wielding the tablet. “Look!”“I saw it,” Cotham said. “I was excited for you to see it.”Only a few pitchers in the sport have seen larger year-to-year increases in fastball velocity than Bowlan, the big man from Western Tennessee who has contributed quality innings for the Phillies.Now, he’s become more important at work.The Phillies put their highest-paid reliever, Brad Keller, on the injured list 90 minutes before Tuesday’s 8-2 win over the Miami Marlins with “right arm tendinitis.” It’s an alarming diagnosis for Keller, who was one of the best relievers in baseball last season but has been erratic at best this season.Interim manager Don Mattingly said the team’s medical staff does not believe it’s serious. “Just probably inflammation,” he said. But Keller has been pitching through the soreness.“It is something that we know has been nagging him,” Mattingly said. “He’s been a little hesitant about talking to us about it. So we don’t need any heroes right now. If we get into September or something and guys want to push through, you allow it. But right now we don’t want that.”Unlike last season, Brad Keller has struggled pitching on back-to-back days. Now he’s on the injured list with tendinitis. (Michael Reaves / Getty Images)Keller had been the setup man to closer Jhoan Duran. Now, Bowlan and Orion Kerkering will be used later in games.Kerkering has been Mattingly’s utility knife; the interim manager has often had Kerkering warming in the bullpen to enter a messy inning. He has stranded nine of his 12 inherited runners. No Phillies reliever has entered more games with runners on base than Kerkering.So, Mattingly could keep him in that role while elevating Bowlan into the eighth inning.Bowlan has a 3.74 ERA in 21 2/3 innings. But he has allowed only one run in his past 12 games (13 innings) with 14 strikeouts and one walk. The 27 hardest pitches of his big-league career (58 games over four seasons) have come this season.The 29-year-old righty is throwing more strikes and is throwing harder.“It’s very interesting,” Bowlan said. “It’s the first time I’ve ever experienced it. And I’m all for that. We’ll see where it goes from here.”Bowlan’s fastballs averaged 95.7 mph in 2025 with the Kansas City Royals, who sent him back and forth to the minors. It’s climbed to 97.3 mph in 2026. Opponents have hit .227 with a .295 slugging percentage against his fastballs.“This year, I don’t know what it is,” Bowlan said. “It might just be here, being here with Philly, or the energy. I mean, it’s a bunch of different things that all get into it. There’s not one specific thing.”He can name a few. Bowlan did different offseason training with a former college teammate named Keith Stepter, who is a strength coach in Tennessee. He credited the Phillies’ athletic training and strength staffs for helping him better understand how his body moves and what work he needs between outings.“They keep you on top of your stuff,” Bowlan said. “You have little tweaks here and there, and they’re always there to help. And it’s consistent. It’s every day. I feel like that’s a big part of it.”Jonathan Bowlan has had one of the larger year-over-year velocity increases in MLB. He’s under team control through 2031. (Orlando Ramirez / Getty Images)Bowlan came over in a trade for Matt Strahm, who has allowed eight homers in 21 2/3 innings for Kansas City this season. The Phillies have not inserted Bowlan into many stressful spots; he’s mostly been a middle reliever. That will probably change with Keller sidelined.Keller’s last outing was a 32-pitch slog in which he allowed three runs on three hits and two walks. It was his most pitches in an appearance since March 28, 2025. Although he’s a former starter, Keller has essentially been a one-inning reliever since May 2025.He adapted so well, so fast last year with the Chicago Cubs that it landed him a two-year, $22 million deal from the Phillies. But it hasn’t been the same. Keller has permitted 14 earned runs this season, already two shy of his total in 2025.Last season, as a full-time reliever for the first time in his career, Keller was exceptional on back-to-back days. He did it 19 times, with three runs allowed in 18 innings. He struck out 24 and walked only three in those outings without rest.It’s been the opposite in 2026; Keller has a 10.50 ERA on zero days’ rest with four walks in six innings.The injury, at least, is something of an explanation for Keller’s ineffectiveness. All of it combined for a certain uneasiness whenever he appeared in close games, especially of late.“(The inflammation) was something that we felt like we’re better off knocking it out right now and not letting it get too far,” Mattingly said. “So we feel good about him. We’re looking at more of the long game with him and making sure that he’s going to be available as we go forward.”The bullpen has been a strength for the Phillies; it has the 13th-lowest ERA in MLB but the lowest FIP and second-highest WAR, according to FanGraphs. The relievers have held leads in tight games.The Phillies are deeper. They recalled Max Lazar, a righty who spent a large chunk of last season with the big-league team, to replace Keller on the roster. They added enough depth to the bullpen group that Lazar became less important.He walked out to the bullpen Tuesday night in the third inning after a drive from Triple-A Lehigh Valley. Then, in a scoreless ninth inning, he threw more than 1 mph harder than he did a year ago.Throwing hard is not everything. But it’s something. After Bowlan fired his 100.2 mph fastball Monday, he went to a 93 mph changeup in almost the same spot. Miami’s Xavier Edwards whiffed at it.“It’s just trusting my stuff,” Bowlan said, “at the end of the day.”