SAN FRANCISCO -- Mark DeRosa gave the San Francisco Giants a two-out, two-strike hit that they've been missing -- and he did it against Phillies ace Roy Halladay.

Manager Bruce Bochy called it one of his team's best at-bats all year. That got San Francisco started, all right.

Eli Whiteside homered and doubled in a run, Jonathan Sanchez struck out six and the Giants beat Philadelphia 5-1 on Monday night to hand Halladay his first loss since joining the Phillies in a blockbuster four-team trade this winter.

"That was huge," Whiteside said of DeRosa's grind-it-out first at-bat. "It got us going in the first, put two on the board and gave everybody a little confidence that 'We can get to this guy.' "

Ryan Howard went 0 for 3 with a strikeout and walk hours after the slugger agreed to a $125 million, five-year contract extension that could keep him with the Phillies until 2017. He flied out to deep center in the first, with Andres Torres going to the wall to make a tough catch.

"When you see that guy and he got that contract, he's got to be happy out there and he's going to swing the bat," Sanchez said. "It's a big ballpark but I thought he hit it pretty good and that it was going to go out. When he caught that ball, it was amazing."

DeRosa hit that two-run single in the first for San Francisco and Aubrey Huff had an RBI single in the sixth after Pablo Sandoval's leadoff double. Sandoval slid home just to just beat the throw.

Whiteside doubled in the second to make it 3-0, then hit a solo homer in the seventh. After Whiteside's double, Halladay (4-1) retired the next 10 hitters in order before Torres dived to beat out an infield single.

Halladay had a six-start winning streak snapped, the second-longest of his career. The right-hander came in with an 0.82 ERA -- third-best in the National League -- but it rose to 1.80.

"We got to one of the best pitchers in the league," Giants reliever Sergio Romo said. "Every game out you have a feeling he's going to go CG [complete game]."

Halladay's three earned runs in the first two innings were as many as he'd given up in his four previous starts combined. He had pitched a five-hit shutout of the Braves in his previous start.

Halladay was tagged for 10 hits and five runs in seven innings, struck out five and didn't walk a batter for the third time this season in a 104-pitch night.

"They come after us. When we play them, they definitely want to beat us," Phillies manager Charlie Manuel said. "They looked better than we did. They had more energy. They were flashy. They were having more fun. I saw that. ... I was hearing today, fans were telling me, that they were having trouble hitting. I won't ever believe that. They came out swinging on him."

Sanchez (2-1), who threw a no-hitter last July 10, labored through five innings. He allowed three hits and one run and walked five. The lefty escaped a bases-loaded jam in the third. He struck out Jayson Werth for the second out, then got Ben Francisco on a shallow fly to right that Nate Schierholtz ran hard to retrieve.

Chase Utley had an RBI groundout in the fifth for the Phillies' lone run, then Sanchez struck out Howard before a walk to Jayson Werth drew a visit from pitching coach Dave Righetti. Sanchez then got Ben Francisco to fly out to left.

Shane Victorino hit his first two doubles of the season and singled for the Phillies, who are in the final series of a nine-game trip.

Halladay had faced the Giants only twice previously, getting a no-decision in his last start against them on June 17, 2004. He's 0-2 against San Francisco, one of four teams he's yet to beat.

"They hit some good pitches and I made some poor pitches that cost me," Halladay said. "They were getting to some decent pitches. Sandoval hit a couple balls that were [on the] chalkline in the batter's box. Learn from it and move on."

The 2003 AL Cy Young Award winner was traded to Philadelphia on Dec. 16 after 12 seasons with Toronto. The swap also included Cliff Lee, who went to Seattle.

The Giants 3 for 7 with runners in scoring position after going 0 for 6 on Sunday. They had been just 5 for 54 with runners in scoring position over the previous seven games.

Game notes

Sandoval is hitting .425 at home (17 for 40). ... Sanchez hasn't allowed a hit to a lefty batter all year in 14 at-bats. ... San Francisco C Bengie Molina had the day off. ... Injured Giants 2B Juan Uribe, nursing tightness in his right elbow, took early hitting and was available to pinch hit. Bochy doesn't expect Uribe back in the starting lineup until at least Wednesday. He still hasn't thrown since leaving early from Saturday's game against St. Louis. ... A moment of silence was held before the national anthem for former Golden State Warriors owner Franklin Mieuli, who died Sunday at age 89. ... Sharks hockey star Dany Heatley threw out the ceremonial first pitch. San Jose is on to the second round of the playoffs.