Cook (1-1, 7.11 ERA), who won a career-high 16 games and was named to his first All-Star game in 2008, struggled through his first four starts this season, going 0-1 with an 8.35 ERA before making an adjustment to correct the release point in his delivery.
That paid immediate dividends on Wednesday, as Cook allowed three runs and five hits in seven innings to lead the Rockies (10-14) to a 7-5 win over San Diego (11-15).
"I knew once I fixed the mechanical part, things would come back to where they need to be," Cook said, noting he had worked with pitching coach Bob Apodaca over the past couple weeks. "Just breaking down my mechanics a little bit and fixing that one little thing made a huge difference.
"If I just keep doing that, I'll be a lot more consistent and give our team a chance to win some more games."
Cook has done just that against the Padres, going 10-2 with a 2.28 ERA in his last 13 starts. He's been outstanding at pitcher-friendly Petco, going 5-1 with a 1.69 ERA in his last seven games there.
"I can't overstate it," Rockies manager Clint Hurdle told the team's official Web site. "He's our guy. He's our ace. You want your No. 1 out there. You want him pitching big games."
Now, Cook will try to help last-place Colorado build on Monday's 9-6 win. The Rockies are percentage points behind Arizona and San Diego, which are tied for third.
Colorado's Chris Iannetta will try to provide some offensive punch again after hitting a go-ahead grand slam in the seventh inning Monday.
"I was just trying to protect with two strikes," said Iannetta, who is 5-for-14 (.357) with three homers and eight RBIs over the last four games. "I was just trying to stay out of the double play."
The catcher has been outstanding over his last seven games against the Padres, going 11-for-22 with four homers and 13 RBIs.
San Diego had cooled considerably since opening the season with a surprising 9-3 record while moving atop the division. The Padres have won just twice in 14 games since, including its current six-game slide.
The Padres haven't dropped seven in a row since Aug. 17-24, en route to finishing at the bottom of the West.
They'll give the ball to Josh Geer (0-0, 5.29), who went 1-1 with a 2.70 ERA in two starts against Colorado last year. That victory - the first of his major league career - came at home on Aug. 30, when he allowed two runs and five hits with five strikeouts in five innings of a 9-4 win.
The right-hander was solid in his last outing on Thursday, giving up four runs and seven hits, including two homers, in six innings of an 8-5 loss at Los Angeles. He didn't get a decision but helped himself by going 2-for-2 with an RBI.
Geer is 2-1 with a 3.68 ERA in eight career games - seven starts.