Irwin pitched seven hitless innings and struck out eight Saturday as the Power coasted to a 9-1 romp over the Hagerstown Suns.
The Pirates' 21st-round pick in last year's Draft issued two walks and faced just one batter over the minimum in his 16th appearance and 13th start of the season. He set down the first eight Suns before walking Sandy Leon in the third. Eury Perez followed with a liner to first base that Aaron Baker turned into an unassisted double play.
Irwin (5-1) ended his night with back-to-back strikeouts, pitching 1-2-3 innings five times.
"I thought I had good fastball command and my curve had a pretty sharp break on it. I was getting a lot of swing and misses with it early," he said. "Once they stopped swinging at that, I started pitching to contact and let them put the ball in to play."
"Around the fifth was when I thought I had a pretty good shot at keeping it going. I never felt like they could beat me. I kept pitching to my strengths -- fastball inside and using my curve."
Ryan Kelly came on to start the eighth and got two quick outs before Brett Newsome homered over the center-field fence.
"I wasn't too worried about it. We had a 9-0 lead when I came out and if we threw a no-hitter it's nice for the team, but I felt bad for our pitcher," Irwin said. "He knows the situation and he wants to pitch well, and I know Ryan Kelly is working hard every day. I thought he pitched well after that."
Newsome's blast was the only hit Kelly allowed over the final two innings as he fanned two.
Irwin won his fourth straight decision and lowered his ERA to 2.44, which would rank sixth in the South Atlantic League if he had enough innings to qualify. "I'm using my change for show, but it's coming along," said Irwin, who was a New York-Penn League All-Star last season. "I think it's come a long way this year. I just have to throw it and throw it with confidence."
Baker went 3-for-5, fell a triple shy of the cycle, drove in two runs and scored twice. Jairo Marquez doubled and collected three RBIs for the Power.
Starter Josh Smoker (3-10) surrendered eight runs on 11 hits over 2 2/3 innings for the Suns, who have lost five straight.