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SAN FRANCISCO -- Both the NL wild-card lead that looked comfortable just a few days ago and the four-run lead that seemed safe at the start of the ninth inning Wednesday night were dwindling with each pitch for the Colorado Rockies.

Then Rafael Betancourt escaped a jam to save the best start of Jorge De La Rosa's career and send the Rockies out of town with a 4-3 victory over San Francisco and a 3½-game lead over the Giants in the wild card.

"Three-and-a-half definitely sounds a lot better in your head than 1 1/2," first baseman Todd Helton said. "It was a big game tonight and we were able to get a win."

It almost wasn't to be as the Giants scored three runs in the ninth and put the tying run on third base before Betancourt struck out Nate Schierholtz for his first save since joining Colorado in July.

That effort made sure that the brilliant work by De La Rosa (15-9) wouldn't go to waste. He allowed three hits in eight scoreless innings to beat the Giants for the sixth straight start. He gave the bullpen a 4-0 lead to start the ninth.

"On the biggest stage of his career, in the biggest game of his career, he pitched the best game of his career," manager Jim Tracy said. "That's exactly what took place tonight. That was as good a game as he has pitched I'll guarantee you in his career. And there have been some good ones."

Troy Tulowitzki and Ian Stewart homered for the Rockies, who had lost four straight games, including the first two in this series. That helped the Giants shave three games off Colorado's wild-card lead, putting a heightened importance on the final scheduled meeting between the teams this season.

But with De La Rosa outpitching All-Star Matt Cain (13-6) and once again dominating the Giants, Colorado leaves town with a comfortable lead with just over two weeks left in the season.

"We're in a situation now where we need to win ballgames," Giants manager Bruce Bochy said. "This was a tough one. We know where we are and we know what is at stake."

The Giants opened the ninth with three straight singles off Franklin Morales, with the first run scoring on Bengie Molina's hit.

Betancourt came in to protect a three-run lead and got Juan Uribe to hit a grounder to shortstop. Tulowitzki's throw to second base was off target for an error, allowing a second run to score and pinch-runner Eli Whiteside to go to third.

After pinch-runner Eugenio Velez stole second, Betancourt got Edgar Renteria to pop up in a rematch of a memorable encounter last month. Renteria's seventh-inning grand slam off Betancourt on Aug. 30 helped the Giants complete a three-game sweep and tie the wild-card lead.

Betancourt got pinch-hitter Randy Winn to hit an RBI groundout and struck out Schierholtz to end it.

"We had drama, obviously, in the ninth inning," Tracy said. "Maybe the save of his career. The start of a career and the save of a career."

De La Rosa (15-9) has overcome an 0-6 start to the season to be one of the top pitchers in the NL the past few months. His 15 wins since June 1 are the most in the majors, with three coming against the Giants.

He was at his best protecting a 4-0 lead in the sixth after the Giants put runners on second and third with no outs. De La Rosa recovered by striking out Andres Torres, Freddy Sanchez and Pablo Sandoval in succession, pumping his fist in celebration.

"The old Jorge from earlier this year or last year wouldn't have done that," Stewart said. "You could see his composure out there. He stayed within himself and trusted his stuff and did a great job."

Cain's second-half woes continued as he has won once in his last 10 starts.

Tulowitzki led off the fourth with his 27th homer for a 1-0 lead. Clint Barmes added an RBI double in the inning and Stewart's two-run shot in the sixth made it 4-0.

"For me it was frustrating putting our guys in a hole after six innings, especially the way De La Rosa has been pitching lately," Cain said.

Game notes

Bochy said he would not tweak his rotation with an off day Thursday. That means reigning Cy Young winner Tim Lincecum will pitch Sunday in Los Angeles and can only make three more starts, instead of four, if he goes on regular rest the remainder of the season. ... Rockies closer Huston Street (biceps tendinitis) threw a bullpen session before the game and will pitch a simulated game Friday. Tracy said Street could pitch in a real game Sunday at Arizona. ... LHP Randy Johnson warmed up for the Giants a day after being activated from the DL but did not appear in the game.