WASHINGTON -- The Giants bullpen had a cause Sunday.

Three pitchers teamed up for four innings of scoreless relief, leading the Giants to a 6-3 victory against the Nationals and, just as importantly, helping Barry Zito pick up his second win of the year.

"The guy is working his tail off," reliever Jack Taschner said. "You see a guy doing that and it feels good to keep his game intact."

It was a hard-fought win for the veteran left-hander, battling through five innings on a muggy and hot Washington afternoon.

"It's definitely tough out there," Zito said. "It just wears you out."

Zito threw 83 pitches in his outing, not showing complete command but also fighting hitters and doing enough to retire them.

He loaded the bases in the fifth, and manager Bruce Bochy could sense that the pitcher was beginning to fatigue, calling on Billy Sadler to warm up in the bullpen. Meanwhile, Zito fought Wily Mo Pena with two outs, getting Pena to strike out on a curveball after he fell behind 0-2 in the count.

"It was sort of a tough day for pitchers. I knew he was getting close there, real close," Bochy said. "If he loses that hitter, we probably go to Billy Sadler there, to be honest."

The Giants also caught a couple of breaks on the offensive end in their four-run fifth inning that gave them the lead.

Kicking off the inning was D.C. native Emmanuel Burriss, who singled, then stole second base after the Washington defender dropped the ball on the attempt to throw him out.

"It was a bang-bang play. I was thinking, 'Wow, I just got thrown out in front of all my family and friends,'" Burriss said. "I've been real successful here -- it's just one of those things."

By the time the batting order came back around to him, he had crossed the plate, along with Steve Holm, Fred Lewis and Jose Castillo, all of whom reached on walks from Nationals pitcher Garrett Mock, who was making his Major League debut.

The Giants were also assisted by the Nationals Park dirt, as Aaron Rowand hit what might have been an inning-ending double play, but the ball hit the dirt and bounced into shortstop Cristian Guzman's face to keep the inning alive, which drew differing reactions from the participants.

"We caught a couple breaks, and we know it," Bochy said.

"I asked him if it hit him in the mouth, and he said no, it was his coconut," Rowand said.

"Not even the ball bounces our way," Nationals manager Manny Acta said of his struggling team.

San Francisco added insurance in the seventh inning with a John Bowker home run to the second deck that scored himself and Ray Durham. Bowker hit his second home run in as many days, though he still hasn't seen his grand-slam ball from Saturday night. In true Washington fashion, the woman who caught it said she'd have to consult her lawyer before trading it for game memorabilia.

From there it was all bullpen. Taschner pitched two dominant innings and recorded two strikeouts, as well as showing off a new mustache.

"I think I'll keep it until the beard grows back," he said.

He added that the heat was helpful in some ways because it allowed him to get a better grip on the baseball, something he's struggled with in recent cold-weather outings.

Keiichi Yabu came on to pitch the eighth, bridging the gap to Brian Wilson in the ninth. Bochy said that pitching Yabu instead of Tyler Walker was a heat-related decision; Yabu was throwing already and he didn't want two pitchers to have to warm up.

The team gets some respite Monday night when the schedule calls for a night game, which is just fine with the Giants.

"If there's a hotter place to play, I'm glad I'm not there," Bochy said.

Zito was also happy he fought through the heat to pick up the victory, something that he says doesn't define him as a pitcher but is important nonetheless.

"He's handled it as well as you can," Bochy said. "It's been getting better, and I think his stuff has really picked up."