After the game, he learned he may have the opportunity for another strong outing next week, too.
Karstens pitched seven-plus stellar innings before leaving with an injury and the Pirates snapped a four-game skid with a 4-0 victory over the Milwaukee Brewers on Saturday night.
Karstens (5-3) gave up seven hits, did not walk a batter and struck out four for his first win in nine career starts against Milwaukee.
"Jeff, tonight, gave us the start that we did need," Pittsburgh manager Clint Hurdle said. "Exactly."
Karstens also had an RBI single and scored during Pittsburgh's four-run fifth inning, but left with what was referred to as an injured right groin after the first two Brewers singled in the eighth.
After the game, Karstens said he thought the problem was more located in his hip than groin. But he said he did not think he was injured seriously.
"Little relieved," Karstens said. "When you're out there on the mound, you don't know how bad it's going to be. I think all the tests came back pretty good -- at least from my standpoint, I thought.
"We'll come in tomorrow and see how it is, but I don't see it being a big issue. I should be able to go in five days."
Pedro Alvarez had two hits for the Pirates, who are one game behind St. Louis for the second wild-card spot.
Aramis Ramirez had three hits for the Brewers, who had won four in a row.
Shaun Marcum (5-4) did not allow an earned run in his first start since June 14 but took the loss due to two errors in the Pirates' fifth.
"Got a little tired there in the fifth inning, but other than that I felt pretty good," Marcum said. "Felt like I was locating from the get-go. In that fifth inning, I made a couple mistakes ... but other than that, for the most part I ended up with close to 90 pitches and I felt like I located the majority of them."
Earlier this season, Karstens spent more than two months on the disabled list due to hip and shoulder issues. He had a setback in coming back from that when he injured his groin in a minor league rehabilitation start but said "this one's nowhere near as bad. I don't see myself missing any time."
Karstens improved to 5-2 with a 3.29 ERA in 11 starts since he came off the DL. No Brewers baserunner advanced past second base while he was in the game.
"The command of all his pitches tonight (was there) -- especially the two breaking pitches," Hurdle said. "He threw some very good splits and some change-ups as well. Just on and off the gas all night. And very efficient... (Karstens) stayed in a real good place with the game, the tempo. Worked quick, low pitch count. All the things you look for."
Closer Joel Hanrahan worked the ninth in a non-save situation, loading the bases before striking out Morgan to close out the Pirates' seventh shutout.
Marcum threw 88 pitches, two fewer than manager Ron Roenicke said was his pitch limit.
"I was real happy with the way he threw the ball," Roenicke said. "The first four innings were outstanding. And really, that inning it was all we totally dropped the ball for him. So I was real happy with him."
Tabata left the game before the sixth with discomfort in his left groin sustained while running the bases. He will be evaluated Sunday. ... The Brewers were held scoreless for the 10th time this season. ... Pittsburgh scored a game's first run for only the fourth time in 23 August games. ... The crowd of 37,460 was the 15th sellout of the season at PNC Park. The ballpark record is 19 in its 2001 inaugural season. ... Bianchi singled in the eighth and ninth innings for his first two major league hits. The Brewers outrighted RHP Mike McClendon to Triple-A late Friday night. ... LHP Erik Bedard will start for the Pirates on Sunday. He allowed five runs in 3 2/3 innings of a June 2 outing against Milwaukee. He is tied for the most losses in the majors (13). The Brewers' RHP Mike Rogers earned his first major league win in his most recent start Monday.