After giving up a pair of first-inning runs, Hahn struck out five over his final three innings, working around two hits and a walk.
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"That's the electric fastball," said catcher Josh Phegley, who hit a solo home run in the fifth. "Everything fed off of that. The curveball was sharper then. That was the fastball he had all last year when he was healthy, and he was lighting it up, so he looked like his old self."
"I think I did well making adjustments in the later innings I threw," Hahn said. "Came out again with a bad tempo, and that was something I wanted to fix after my last start. I did a poor job at it again, but once I got back in my rhythm and locked in on my fastball, things started going a lot better for me.
"For me, it might just be a warmup routine. I think I'm just a little slow getting used to things again right now, and I think I have to do a better job in the bullpen prior to going out there, maybe increasing the intensity a little bit."
That became the plan after the first inning, Phegley said.
"I feel like he's feeling out his release and trying to make sure he feels healthy, and I think that's kind of been his problem here recently," he explained. "I'm just glad he found that tempo and rhythm and got back to his old self."
Hahn's changeup remains a work in progress, and he threw only a small handful of them Friday, when he was forced to narrow his focus on his fastball -- "my best pitch, my most important pitch," he said.
It could be even better this year, after Hahn used the offseason to strengthen his lower half in order to ease the stress on his arm.
"The ball seems to be coming out of my hand better with less effort," said Hahn, who went 6-6 with a 3.35 ERA in 16 starts before his injury last season.
"The sky's the limit for him," Phegley said. "He's got a lot of talent, a great arm, and he's got the stuff to do it. He's consistent in the strike zone, and with that kind of aggressiveness and intensity on the mound, with that velocity and breaking ball he has to work with, he's got all the pieces there."