WASHINGTON -- Bryan Petersen helped make sure his big league debut was a winner.
Petersen sparked the decisive eighth-inning rally with a pinch-hit single in his first career at-bat and Gaby Sanchez had a tiebreaking single, lifting the Florida Marlins to a 4-2 victory over the Washington Nationals on Friday night to end a three-game skid.
"That's pretty good for (Petersen) -- a kid who just came up (to) get his first at-bat, first major league game, getting a knock," Florida manager Fredi Gonzalez said. "That's got to be a thrill. Good for him, and it's good that we got a win because it's nice to celebrate also his first major league hit and a win."
Petersen, whose contract was purchased from Triple-A New Orleans on Friday after the Marlins designated infielder Mike Lamb for assignment, singled off Brian Bruney (1-2) leading off the eighth. Petersen moved to second when Bruney fumbled Chris Coghlan's bunt attempt for an error and Sanchez followed with a looper to shallow right-center, breaking a 2-all tie.
"It was an awesome experience," Petersen said. "I was just trying to get on base. I was nervous, obviously. I was just trying to slow the game down, just try to stay in the moment, take it pitch-by-pitch."
Bruney, acquired in an offseason trade from the New York Yankees, has been ineffective in a setup role. The right-hander has a 6.00 ERA and has issued 18 walks in 15 innings.
"I'm being aggressive and they're just fighting off some tough pitches and getting me deep in counts," Bruney said. "When the time to make a pitch has come, I'm not making that pitch. It's something I need to get better at, cut down those walks and keep guys off base."
Marlins right-hander Chris Volstad (3-2) went seven innings, yielding four hits and two runs. He walked two and struck out four.
Leo Nunez worked the ninth for his fifth save in seven chances.
"Volstad was the game," Gonzalez said. "He got stronger as the game went on. He made those guys swing the bats."
The right-hander, who threw a four-hitter against Washington in his last start May 2, wanted to pick up where he left off.
"Getting swept in a series, you want to start the next one off right," he said. "I really wanted to go out there and do that for the team -- just to try and shut down the Nats and try to get back on the winning side of it."
But the Nationals loaded the bases in the first inning and grabbed a 1-0 lead on Josh Willingham's fielder's choice grounder.
Ryan Zimmerman ripped Volstad's 2-1 changeup into the center field stands with one out in the fifth. The solo shot, his fifth homer, made him 8 for 15 with two home runs in his career against the right-hander.
Cantu responded with his seventh homer, a line shot to left-center with one out in the seventh that snapped an 0-for-19 slump, and the Marlins knocked Nationals starter Craig Stammen from the game two batters later when Baker tripled.
Stammen allowed two runs -- one earned -- on four hits over 6 2/3 innings. He struck out a career-high eight.
"They gave me the lead twice and I gave it up twice," Stammen said. "That's on me."
Baker's triple was the first of his 193-game career. ... After the game, the Nationals optioned OF Justin Maxwell to Triple-A Syracuse. LHP Matt Chico is expected to be recalled from Double-A Harrisburg to start Saturday afternoon. ... Desmond's error was his team-high fifth.