PITTSBURGH -- A detour to the bullpen has made Lance Lynn a better starting pitcher.

Lynn allowed only an inside-the-park homer to Alex Presley in seven innings, leading the St. Louis Cardinals to a 4-1 victory over the Pittsburgh Pirates on Friday night.

Filling in nicely for injured ace Chris Carpenter, Lynn (3-0) gave up four hits. He walked one and struck out four. He has won each of his starts this season and compiled a 1.42 ERA while Carpenter has been on the disabled list with a nerve problem in his pitching shoulder. Lynn pitched primarily in relief last season as a rookie when St. Louis won the World Series.

"What I did when they moved me to the bullpen last year was challenge hitters, get ahead in the count and make them hit my pitch," Lynn said. "When I was starting, I tried to nitpick. I'd get behind in the count and have to give the hitters good pitches to hit. I learned a lot from pitching out of the bullpen. I'm more aggressive and more confident now as a starter."

Lynn showed that aggressive approach against Pittsburgh as he needed just 88 pitches to get through seven innings. He allowed four hits and one walk while striking out four.

"Efficient is the right word," Cardinals manager Mike Matheny said in describing Lynn's outing. "He had good life on the ball and later in the game he really mixed in all his pitches. He had a good tempo, a good rhythm with [catcher Yadier Molina]. He really kept them off balance."

Presley led off the bottom of the first with a drive off the top of the center field fence, the ball just eluding a leaping center fielder Skip Schumaker. Jack Wilson hit the Pirates' only other inside-the-park home run at PNC Park on July 2, 2004, and the last Pittsburgh player to hit one was Freddy Sanchez at Houston on July 21, 2008.

"I wasn't expecting it," Presley said. "I thought I had a triple for sure, and when I saw him miss it, I think he got hurt out there and couldn't get up, that helped my chances a bunch. It was one of those things."

Schumaker, who said he thought he would be able to play Saturday, was shaken up on the play and left the game. He had been activated from the disabled list prior to the game after missing the first 13 games because of a strained right oblique.

"Obviously it was not the debut I was looking for," Schumaker said with a half-smile. "First of all, I should of caught the ball. Second of all, I couldn't breathe. Coming off an oblique injury and getting your ribs rattled wasn't something you wanted to do. They pulled me as a precautionary measure. I felt I could have stayed in but it is what it is."

Jose Tabata followed Presley's homer with a single but Pittsburgh never put a runner in scoring position.

"You get an inside-the-park homer and drop a single to the next guy and we ended up with two more [hits] the rest of the night," Pirates manager Clint Hurdle said. "It was another strong outing for [Lynn]. You have to take the barrel to him. He doesn't seem like he's going to hurt himself."

Lynn also scored the go-ahead run on Carlos Beltran's two-out single in the fifth inning off Charlie Morton (0-1).

Daniel Descalso homered for the NL Central-leading Cardinals, who won for the fifth time in six games.

Morton allowed two runs -- one earned -- and four hits in five innings with three walks and six strikeouts.

Mitchell Boggs and Jason Motte, who notched his third save in three tries, each pitched a hitless inning to complete the four-hitter for St. Louis.

After St. Louis tied it in the second inning on Molina's RBI double, Lynn led off the fifth with a single. He took second on Rafael Furcal's groundout, advanced to third on Matt Holliday's fielder's choice and scored on Beltran's line hit to right field.

Descalso homered -- a liner into the right-field stands -- in the eighth off Jared Hughes to start a two-run inning. Furcal added a run-scoring double.

Notes

• Schumaker was activated and 1B Lance Berkman was placed on the 15-day DL with a strained left calf. Schumaker's rehab assignment at Triple-A Memphis was cut short after four games because the Cardinals needed someone to fill in for CF Jon Jay, who sprained his right shoulder on Thursday and is day to day. Schumaker was 3 for 13 (.231) with two walks and two strikeouts at Memphis.
• Pittsburgh RHP Jeff Karstens, who was removed from his start after one inning Tuesday and placed on the DL, will rest seven to 10 days before beginning a throwing program. The Pirates do not have a timetable for Karstens' return. RHP Brad Lincoln is expected to start in Karstens' place Monday night against Colorado.
• Jake Westbrook (2-0, 0.64) will start for St. Louis against Kevin Correia (1-0, 1.50) on Saturday night. Westbrook is 0-3 with a 5.46 ERA in four career starts against the Pirates.