SAN FRANCISCO -- Brandon Belt took a couple of steps out of the batter's box and admired his towering flyball a little bit too long. When the ball hit off the top of the wall and Belt started running, it was too late. He was thrown out at second base.

His teammates, though, could laugh it off considering what Belt has accomplished this month.

Madison Bumgarner pitched a five-hitter and Belt had three hits and three RBI, leading the San Francisco Giants to a 6-1 win over the Washington Nationals on Tuesday night in a matchup between NL division leaders.

Belt has more hits in August (17) than he did in any previous month and is hitting .472 so far.

"It's quite a game he had," Giants' manager Bruce Bochy said. "I guess he went with the theory of keep running until they throw you out."

Belt was also thrown out trying to stretch his second inning, RBI double.

"That's good hitting and some tough luck," Giants outfielder Hunter Pence said. "He's had some huge hits for us and he got us on the board early."

Bumgarner (13-7) struck out six and walked one in his second complete game this season.

Pence and Marco Scutaro, both acquired before the July trade deadline, each added three hits for the Giants, who have won three of four at home after losing eight of nine.

Pablo Sandoval, in his first start since coming off the disabled list Monday, Angel Pagan and Brandon Crawford also drove in runs.

"It's a great lineup and we have a lot of potential," Pence said. "The big thing is the way Belt and Crawford have been swinging the bat. They have been a huge part."

Adam LaRoche drove in a run for the Nationals, who have won 11 of their last 14.

NL ERA leader Jordan Zimmermann (9-7) had his six-game winning streak come to an end after allowing two runs on eight hits. He walked two and struck out four.

"I didn't have my best stuff that's for sure," Zimmermann said. "I was missing here and there a little bit. I just wasn't getting the misses."

Zimmermann has allowed four or fewer earned runs in all 24 starts this season, including 18 of two or less.

"I thought Jordan threw the ball good," Nationals' manager Davey Johnson said. "I've seen him throw better, but Bumgarner was just too tough."

Bumgarner lowered his NL-leading home ERA to 1.85 with his second complete game of the season.

"You always want to finish and my teammates took the pressure off and made it easier," Bumgarner said. "There's no time to be thinking about anything but pitching."

Pence singled leading off the second and scored when Belt followed with a double. Belt was thrown out trying to stretch it into a triple.

Belt also singled home a run in the sixth. The ball bounced right to Jayson Werth, who made a strong throw that nailed Belt at second.

The Giants added four runs in the eight on RBI from Sandoval, Belt, Crawford and Pagan.

Werth tripled and scored on LaRoche's single in the seventh for the Nationals.

Notes

• Giants RHP Brad Penny was placed on the DL with a right shoulder impingement. RHP Dan Otero was recalled from Triple-A Fresno.
• RHP Tim Lincecum (6-12, 5.35) pitches for the Giants on Wednesday. He is 1-3 with a 5.36 ERA in seven games against the Nationals.
• Scutaro recorded his sixth game of at least three hits this season.
• Giants RHP Shane Loux (neck strain) pitched an inning, with one strikeout, in his first rehab appearance with Fresno.
• Giants OF Melky Cabrera is five hits shy of 1,000.
• Bumgarner is 16-0 when given five runs or more of support.
• RHP Stephen Strasburg (13-5, 2.90) pitches for the Nationals on Wednesday. He leads the NL with 11.2 strikeouts per nine innings.
• Nationals INF Ian Desmond (left oblique strain) could be activated as early as Friday.
• Washington OF Michael Morse was out of the lineup with a jammed right thumb.