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DENVER -- When traffic filled the bases, Aaron Cook's sinker was superb as the pitch dipped and dropped to bail him out of trouble.

Cook relied heavily on his trademark pitch to win his seventh straight decision Sunday, leading the Colorado Rockies to a 4-2 victory over the San Francisco Giants.

Cook gave up nine hits in seven innings, yet always seemed to wiggle off the hook as he allowed just two runs.

"It's not the end of the world if somebody's on," Cook said with a shrug. "I really don't worry about guys on base. Once they're on, what am I going to do?"

Let his defense go to work.

The Giants rolled into 16 groundouts, including a double play in the fourth that thwarted a potential rally.

Cook (10-3) has now forced 17 double play this season, which ranks among the NL leaders.

"He's got one of the best [sinkers] in the game and good command of it," Giants manager Bruce Bochy said. "When you're facing a guy like Cook, you know you have your work cut out."

For a series in July, this almost had a playoff vibe to it. And by taking two of three, the Rockies increased their NL wild-card lead to two games over the Giants.

Sure, there's still a lot of games left. But Rockies manager Jim Tracy said this was vital for momentum as the team heads out on a 10-game road trip.

"We leave here feeling very good about ourselves," Tracy said.

The Giants, meanwhile, return home with a sinking feeling. Asked to describe the team's 3-7 road swing, Travis Ishikawa simply said, "Awful."

San Francisco had Cook on the ropes a couple of times, but couldn't deliver the clutch hit.

For that Cook can thank his diving sinker.

It helped him work out of trouble in the fourth after Pablo Sandoval and Ishikawa led off with singles. Cook enticed Edgar Renteria into a 4-6-3 double play. Then Clint Barmes helped Cook out by diving for John Bowker's grounder between first and second, popping up to a knee and throwing John Bowker out by a stride.

"We definitely had our opportunities. We had guys on base," Ishikawa said. "It's always frustrating. Anytime you've got guys on base you want to drive them in."

Cook's focus doesn't seem to falter with runners on base. It's a trait he's honed over the years.

"I know I have good enough stuff that I can continue to throw my sinker," he said. "Sooner or later, they're going hit it at somebody. My guys are good enough they're going to make great plays behind me."

Batting leadoff, Seth Smith got the Rockies started. He drew two walks, singled, scored two runs and stole a base.

All in a day's work.

"If I get on base it's a successful at bat," Smith said.

Ryan Sadowski (2-3) turned in his shortest stint this season, leaving after just 2 2/3 innings as he gave up three runs and five hits.

The right-handed rookie was pulled in the third after loading the bases and allowing a run-scoring sacrifice fly to Tulowitzki, followed by Ian Stewart's RBI single. Justin Miller came in and got Carlos Gonzalez to pop up and end the inning.

"[Sadowski] was pitching behind and worked hard out there, ran a lot of deep counts, pitch count got up there," said Bochy, explaining why he pulled Sadowski early. "That was his biggest issue. The bullpen, what a great job they did. Gave us a chance to come back. We just have to get this offense going."

Game notes

Bochy said OF Aaron Rowand (bruised right forearm) will likely have an MRI on Monday. "We're going to do some tests tomorrow to see if there's something more in there," Bochy said. Rowand had a pinch-hit double in the fifth. ... San Francisco C Bengie Molina was given the day off. ... Rockies RHP Jason Marquis said the blister on his middle finger was feeling better and that he'd start Tuesday night in New York against the Mets. ... Colorado has 42 sacrifice flies this season, the most in the majors. ... The Rockies have now won 10 straight over rookie pitchers this season.