Well, he won't be returning to the rotation just yet, confirmed manager John Russell afterward, but there was little question that Karstens stepped up in significant fashion.
In what was supposed to be Charlie Morton's anticipated debut with the Pirates, Karstens stole the show with a dominant relief appearance that propelled the Pirates to a 3-2 win at Turner Field on Wednesday night. The victory snapped the Pirates' three-game losing skid, one that included consecutive one-run losses to the Braves already this series.
"He did a great job," Russell said. "He saved us a lot of headaches. He did a phenomenal job to do what he did to save our bullpen."
All the hoopla about Morton starting against an Atlanta team that included him in a four-player trade to acquire Nate McLouth a week ago lasted just four hitters. Granted, Morton was effective in the first inning, throwing 13 pitches and allowing just one hit. But that inning would be his last.
Morton felt his left hamstring tighten while doing some pregame stretching, and though it didn't bother the right-hander on the mound, there were concerns about his ability to field and cover first. Consequently, the Pirates took the cautious route.
"[It was] very disappointing," Morton said. "I was anxious coming back here to Atlanta and hopefully get some quality innings in. It's unfortunate."
In came Karstens, who had one day earlier been pushed into the bullpen in order to make room for Morton in the rotation. He and pitching coach Joe Kerrigan had also already agreed before the game that Karstens' limit would likely be just one inning if he was needed on Wednesday.
Karstens had already thrown a 20-pitch bullpen session earlier Wednesday afternoon. He had thrown a side on Tuesday. And he had thrown 18 pitches in an emergency relief appearance in the Pirates' 15-inning game on Monday.
"When it came down to it, I had to do what I had to do to save our bullpen," said Karstens, who lasted 4 2/3 innings in the game. "I'm used to throwing a lot, and I'm glad to say my arm is intact."
Whether it was simply responding to the Pirates' need for him to preserve the rest of the bullpen or doing his best to erase the bitter taste of Monday's appearance -- in which he was tagged with the loss -- Karstens responded to the call.
As it would turn out, Karstens ended up having arguably his strongest performance of the season. He was exceptionally efficient, allowing just four hits and one run. He didn't walk a batter and went to a three-ball count just once.
"Their guy on short notice pitched great," Braves manager Bobby Cox said. "He threw nothing but strikes. I mean, a ton of strikes."
Indeed, as 43 of Karstens' 59 pitches went for strikes. He relied heavily on his fastball to combat an aggressive Braves lineup.
"He's just a grinder," first baseman Adam LaRoche said. "He knows he's not going to blow it by them, but just gets it done."
Karstens' stellar effort helped spare a bullpen that combined to pitch 8 1/3 innings in Monday's loss from being exhausted two days later. And it left others wondering: Has Karstens put himself back in position to reclaim that fifth rotation spot? Russell defused that speculation immediately.
"It will be Morton," Russell said. "That was pretty electric stuff that first inning. I wish we could have seen more of it. Hopefully we can get over this strain and he can continue to start."
Karstens left the game after allowing an RBI double to Braves catcher Brian McCann on a ball that hit the top of the outfield wall in left-center field. Prompted to do so by Cox, umpiring crew chief Dana DeMuth used instant replay to confirm that McCann's hit was not a home run.
"More than anything, I wanted to throw well tonight to get over the last outing that I had," said Karstens, whose relief appearance was the longest by a Pirates pitcher since Shawn Chacon pitched five innings out of the bullpen in May 2007. "That wasn't me. I was in a situation the other night that I wasn't really comfortable with."
While Karstens was minimizing the bullpen's work, the Pirates' offense stung Braves starter Jair Jurrjens for two third-inning runs on an RBI groundout by LaRoche and a two-out RBI single by Jason Jaramillo.
It would then be some aggressive baserunning by Craig Monroe that helped the Pirates tack on an insurance run in the seventh, a run that proved to be pivotal when closer Matt Capps served up a solo homer with two outs in the ninth.
Standing on second after being hit by a pitch during a pinch-hit at-bat, Monroe moved to third when LaRoche hit a grounder up the middle. The ball was fielded by Braves second baseman Kelly Johnson and flipped to shortstop Yunel Escobar to try and get a forceout at second. Freddy Sanchez was ruled safe.
As Escobar took the throw, Pirates third-base coach Tony Beasley waved Monroe home. Escobar held onto the ball, paying no attention to Monroe, and had no chance to get him at the plate once he realized Monroe was still running. The run put the Pirates ahead, 3-1.
"Tony did a great job at third taking a chance right there," Russell said. "That's a good job by the third-base coach to take a chance there and keep the runner moving. Obviously that was a big run for us."
Before Capps sealed his 14th save of the season, Sean Burnett and John Grabow combined to pitch 2 1/3 innings of scoreless relief.
Jenifer Langosch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.