PITTSBURGH -- For a second straight start, the second inning proved to be a stumbling block for Nationals starter Jake Irvin.

After pitching a strong first with an early three-run lead, Irvin allowed five runs in a crucial second, and the Nationals fell to the Pirates, 9-4, on Thursday night at PNC Park.

Irvin got a quick groundout from Rowdy Tellez to lead off the inning, but then he walked back-to-back batters on borderline ball fours. The first three RBI knocks Irvin allowed came on curveballs thrown in the first two pitches of each at-bat. By the end of the night, six of the seven hits Irvin afforded came on that offering, and manager Dave Martinez sensed he was going back to the pitch too much for comfort.

“When he starts going to the breaking ball quite a bit, he gets in trouble,” Martinez said. “I like his two-seamer. His two-seamer works really well. We’ll talk to him tomorrow about keeping things simple, especially when you give up three runs like that.

“Attack, let the defense play, keep the ball down and attack the hitters. That’s when he’s really good.”

Of the 46 pitches Irvin threw in the second inning, 19 were curveballs (41.3%) -- nearly as many as his four-seamer (13) and two-seamer (nine) combined.

“There have been times this season where mixing it up from the jump has been successful, and I think that’s something we’ve tried to make the M.O.,” Irvin said. “But at the end of the day, establishing the fastball is part of that, and I think there just has to be a little more emphasis on that.”

Irvin allowed seven runs in the second inning of his prior start against the Cubs, which provided all the runs the Cubs needed to edge the Nats by one run in a 7-6 game.

“It’s something we’ve tried to limit all year long,” Irvin said of the big innings. “I think I’ve just done a really bad job of establishing the fastball. That’s something that keeps guys honest on the offspeed pitches. Guys are getting good pitches to hit, pitches in the zone, especially in good counts for me. I’ve got to be better about making better pitches deep in the count to those guys.”

But just like he did against Chicago, Irvin was able to bear down after a heavy workload in one inning to avoid an overly abbreviated start. He allowed one more run in the third inning on Thursday but completed five innings -- a mark which was far from a given for him to reach when his pitch count sat at 58 pitches after two innings.

“It was good to see him go back out there and to see him finish up the way that he did was great,” Martinez said. “He threw up some zeros for us. … We were a little concerned about sending him back out, but I’m glad we did. Our bullpen, we had some guys who needed a break, and they got that. So we should be fresh.”

Just like Irvin bounced back to end his outing on a better note, he’s looking to put a wrap on his 2024 season with a few better starts and go into the offseason in a good spot. Following a strong first half, in which he had a 3.49 ERA in 20 starts and garnered some All-Star hype, he’s pitched to a 6.12 ERA in nine starts since the break.

“I’m trying to take this day to day and not to be discouraged by any results recently,” Irvin said. “I think that things could have gone one way or another in the past few starts on one or two pitches, so it’s eliminating those bad pitches and finding ways to get guys out, get outs early and get deep in the ballgame like we were earlier in the season.”