Clint Hurdle gave him some extra time. A rainout Tuesday helped even more.
"He's fresh and he's ready and he's coming off a large volume of pitches," Hurdle said.
Ohlendorf left his last start Friday during the third inning due to a strained shoulder, and he was replaced by Karstens. Karstens promptly threw 3 1/3 scoreless innings, allowing the Pirates to stay in a game they ultimately won 4-3 in 14 innings.
That was typical for Karstens, who has served in a variety of roles for Pittsburgh since being acquired in a trade from the New York Yankees in 2008. Karstens made 41 starts over his first 2 1/2 seasons with the club, and he's also made 36 relief appearances ranging from long man to set-up guy.
"I've had several conversations with him, and I know he doesn't have an agenda," Hurdle said. "Most players have an agenda. He wants to pitch."
Karstens originally was to pitch the series finale against Milwaukee on Thursday, but the rainout pushed him back into the weekend series in Cincinnati.
The Pirates and Brewers pushed back their starters for the series. That means that Milwaukee's Shaun Marcum will face Kevin Correia Wednesday instead of Tuesday, and the Randy Wolf-Paul Maholm matchup is bumped back to Thursday.
The makeup date for Tuesday's scheduled game will be announced at a later date.
The Brewers got plenty of good news on the unscheduled day off. Two of their marquee players on the disabled list took significant steps in their return.
Greinke threw a 25-pitch simulated game in a batting cage Tuesday in his latest step to return from a cracked rib.
The 2009 American League Cy Young award winner, Greinke was acquired from the Kansas City Royals in a December trade in the hopes he'd be Milwaukee's ace. But he injured himself playing pick-up basketball early this spring and opened the season on the disabled list.
"He got after it," Roenicke said. "He threw the ball really well."
Greinke had thrown two bullpen sessions last week.
"I threw and feel healthy so that's good," Greinke said. "It's just getting ready, and you just have got to do these things to be ready, and then go do another one and then a couple games, and hopefully be ready then to come back."
Greinke likely will throw more pitches in another simulated game Friday.
"If he comes out (Wednesday) and he's not sore, I will be pretty impressed because he wasn't holding back on anything," Roenicke said.
Hart's return from a strained left oblique sustained during spring training took another step forward when he took live batting practice in a cage for the first time.
Hart, who over the past weekend threw and participated in outfield drills, reported no setbacks immediately after the batting session.
"He looked good swinging," Roenicke said.
The loss of Greinke and Hart so early in spring training tempered some of the enthusiasm the Brewers had heading into the season. An 0-4 start didn't help, but Milwaukee has won five of six since as it embarks on what was supposed to be a nine-game road trip.
Over the past seven games, slugging first baseman Prince Fielder led the majors with 11 RBIs and 21 total bases while batting .440 (11 for 25) with two homers and four doubles, earning NL player of the week honors.
Pirates RHP Evan Meek (right shoulder tightness) will be available Wednesday for the first time in seven days. ... Pirates LHP Joe Beimel threw an inning of relief for Triple-A Indianapolis. "The reports are his command has been good," Hurdle said. "We'll see how he feels (Wednesday) or Thursday."