Pittsburgh's pitchers are feeding off each other's success these days.
Karstens allowed one run and three hits for the Pirates, who lead the league in ERA and have won four of their last five games. Sanchez finished with three hits.
"A lot of people doubted us, but we all believe in ourselves and we all believe in each other," Karstens said of the staff that has a 3.00 ERA so far this season after finishing with an NL-worst 5.10 ERA last year. "That's all that matters right now. Enough can't be said for [new pitching coach Joe Kerrigan]; we're more prepared than any team in the league."
Ohlendorf allowed two hits over seven innings as Pittsburgh beat Florida 8-0 on Monday for its third shutout in four games. The Pirates have four shutouts this season; the other 13 NL teams have combined for six. Pirates starters have allowed more than two runs in four of their 14 games.
"Those guys are giving us a chance to win ballgames," shortstop Jack Wilson said.
Cameron Maybin hit his first National League homer for Florida, which has lost two straight against the Pirates after opening the season with an 11-1 stretch.
Matt Capps pitched the ninth for his fourth save.
Karstens (1-0) won for the first time since Aug. 6, when he took a no-hitter into the eighth inning at Arizona. Karstens, acquired from the New York Yankees in the Xavier Nady trade in July, didn't allow a run in his first two Pirates starts but had been 0-6 since.
"He kept the ball down and did a nice job," Pittsburgh manager John Russell said. "He got through six, which is pretty solid start for him at this point of the season."
The Pirates scored in each of the first three innings to build a 3-1 lead. Adam LaRoche drove in Nyjer Morgan with a first-inning single, and Jason Jaramillo picked up his first major league RBI with a run-scoring double in the second.
Sanchez led off the third with a drive to left-center off Anibal Sanchez (1-1). The 2006 batting champion is hitting .476 (10-for-21) over his last five games.
Maybin got Florida within one with a leadoff shot in the eighth that traveled an estimated 447 feet. The Marlins put two runners on later in the inning but John Grabow retired Hanley Ramirez on a popup and struck out Ross Gload to end the threat.
"It's funny, we were off to such a great start, everybody had been kind of used to slapping hands after the game," Florida second baseman Dan Uggla said. "These days are going to happen to you. You're going to run into some pretty good pitching day in and day out."
Ramirez doubled in John Baker in the third for Florida. Sanchez allowed three runs and seven hits in seven innings.
"He got better as the game went on," Marlins manager Fredi Gonzalez said. "He got stronger as he threw. The velocity was there, the life on his fastball ... he pitched out of a couple jams early and only gave up one run each time.
"We just didn't hit. We had some opportunities to score some runs with the right people up, but we just didn't hit. That's the way it goes sometimes."
- Marlins 1B Jorge Cantu was scratched with a sore wrist. Gload took his place at first base and in the cleanup spot in the lineup.
- Pittsburgh's Andy LaRoche has eight hits in his past 19 at-bats after beginning the season in a 0-for-18 slump.
- The announced crowd was 9,917, but the number of fans in the seats was less than half that on a cool, soggy night in which the city's sports attention was with the NHL Penguins, who beat the Flyers 3-1 in a playoff game in Philadelphia.