By late June, his ERA had climbed to 5.05 and he began looking for answers.
"The transition was pretty bad," the Pirates prospect said. "I started off struggling a lot, my first five or six starts, and it kinda made me step back and look at what I was doing, why I wasn't having success like I did last year."
Irwin, though, has been reborn. A refined changeup and a cleaner delivery helped him record his third straight complete game Friday night as he held New Hampshire to two hits over seven innings in a 1-0 win in the first game of a doubleheader.
The 25-year-old right-hander struck out a season-high nine batters, allowing a single in the first and a double in the fifth before finishing with back-to-back punchouts.
"It's been really good [lately]," said Irwin (3-7). "I had really good fastball command and my curve has been my money pitch. I've been able to throw it for strikes and bounce it when I need to. My change is thrown into the mix and it's not a great pitch, but it's getting outs when I need to."
The gem marked the fifth time in six starts in which Irwin has allowed one run or fewer. He's gone at least six innings in all six of those outings and has allowed only three earned runs over 22 innings in his three complete games.
The University of Mississippi surrendered at least three runs in five of his first eight starts after going 8-4 with a 3.81 ERA in 15 starts for Altoona last season. He reviewed his delivery and looked into his changeup. Since June 29, he has not allowed more than one earned run in any outing.
"That's where my changeup came into play," Irwin said. "A couple mechanical tweaks and things start coming together. My arm was late, I had to make sure I was releasing my breaking ball at the top and getting on top of the ball, making sure the ball is down."
Despite rising to Double-A by his third season, Irwin doesn't appear in any of the Pirates' top prospect rankings. The 6-foot-3 righty was a 21st-round pick in 2009 and has worked his way up from short-season State College.
New Hampshire's only success came on Ryan Goins' two-out single in the first and Brian Van Kirk's ground-rule double in the fifth. Irwin also worked around a leadoff walk in the fourth, stranding Jake Marisnick at third by striking out Brad Glenn.
"I think my confidence is through the roof right now," he said. "With each outing, I'm going out there and taking it one batter at a time. Especially with back-to-back complete games, I've gotta attack in the first inning and then just keep going. If I throw seven again, so be it; I just want to give my team the best chance to win and, tonight, one run was all we needed."
Irwin struck out Glenn and Kenen Bailli to end the seventh and wrap up the Curve's sixth shutout.
"That felt great," he said. "I was making sure I wasn't giving them anything to hit, trying to make them hit whatever I wanted them to. One was a fastball away looking, the other was a curve in the dirt to end the game."
Altoona put Irwin in position to win it when Stefan Welch singled home Oscar Tejeda with one out in the second.
Irwin said there was no talk about not finishing the game.
"My pitch count was low, I was in the 70s or so before I went out there in the seventh, so I just assumed I had it," he said. "I was able to beat them with my curve, so it was nice."
Eastern League All-Star Yohan Pino (5-6) also went the distance for New Hampshire, striking out nine while yielding a run on five hits.