CINCINNATI -- The Pirates had essentially knocked themselves out of the game by the end of the first inning in Game 2 of their doubleheader with the Reds on Monday, but there were still positives to draw from their 8-1 loss.

The main takeaway? Rookie Mitch Keller, making his Major League debut as a spot starter in this twin bill at Great American Ball Park, pitched well after a mostly disastrous opening inning.

• Box score

“The entire volume of work, I saw improvement,” manager Clint Hurdle said. “He got punched hard early. And the hole was awful deep that was dug. From that point on, everything got better. The fastball was up, the breaking ball was up, the changeup was up. They hit it hard. After that, he responded well.”

The Pirates placed no inflated expectations on their prized pitcher, the club’s No. 1 prospect, according to MLB Pipeline, when they announced he would start Game 2. In fact, they made it clear ahead of time this was probably too early in Keller’s development for a promotion, and this was happening only out of necessity -- their rotation and bullpen have been severely affected by injury and inconsistency, and they needed to dip into their system for a starter to help out during what was surely going to be a very long day at the ballpark.

And at first, it looked as if Keller may not make it out of that opening frame, which could have spelled disaster for the Pirates. They used four relievers in their Game 1 win, and even with the extra arm in the 'pen due to the 26th man rule, absorbing seven or eight innings would have been a struggle for any team, doubleheader or not.

• Three takeaways from Pirates' comeback win in Game 1

But Keller, the Pirates' second-round Draft pick in 2014, settled in well, retiring eight batters in a row and allowing just one hit over his final three frames.

“I think just the first inning, I was a little amped up,” Keller said. “My offspeed pitches weren't as crisp as the second, third and fourth innings. I think that was the main thing. My fastball the first inning was pretty much the way it was the whole game.”

Keller, pitching in front of nearly 40 friends and family who made the trek from Iowa to watch his debut, faced 11 batters in the first inning. He issued walks to two of the first three, before logging his first Major League out -- a strikeout of cleanup hitter Derek Dietrich. The dagger arrived two batters later, when Jose Iglesias launched a grand slam, putting the Reds ahead, 5-0.

“Changeup,” Keller said of the pitch to Iglesias. “Just a bad changeup.”

But Keller needed just 12 pitches to retire the side in the second, and he ended his 85-pitch outing with seven strikeouts.

The performance impressed at least one of the hitters he faced.

“He’s good. He’s got good stuff,” Dietrich said. “There’s no doubt about it. You saw some flashes. I didn’t see him the first at-bat very well. The second at-bat, I was like ‘one, two, three [snaps his fingers]’ and he just dotted three different pitches.

“He showed flashes like he’s got the stuff. Once he settles in and finds the routine and everything falls into place, he’ll probably be a top-of-the-line starter for them. Tough first go for him, of course. At least he got me with his first K, which sucks for me but for him, it’s all good.”

Keller threw north of 40 pitches in that opening frame, and had he not struck out Jesse Winker to end the rally, he probably would not have been given the chance to go out for the second.

Instead, Keller stayed in, which shaved several innings off the bullpen’s workload.

“The man's got an arm that you’ve got to take care of,” Hurdle said. “[Winker’s] his last hitter. If he doesn't get that guy out, he's out of the game, and we have to make up seven innings. We've got to find a way to patch that together, which we would have done. He got the man out and moved on. There was resilience, there was fight back.”