De La Rosa struck out six and didn't let a runner reach scoring position in seven scoreless innings, and Rockies pitching posted its sixth shutout of the season, 4-0 over the Giants at Coors Field.
A little less than a month ago, De La Rosa (8-7) was removed from the rotation. But since Aug. 1, he is 3-1 with a 1.78 ERA in five starts and two relief appearances.
In his sixth organization, counting a stop in the Mexican League, and with his third Major League team in four years, De La Rosa, 27, is finally turning his considerable talent into production.
"I heard it when I was a player -- sometimes left-handers take longer to pop," Rockies manager Clint Hurdle said.
The Rockies are desperately trying to keep their playoff dream bubble from bursting.
Of course, the way things have been going lately, it didn't gain them any ground. The D-backs rallied from a three-run deficit to beat the Cardinals, 8-6, on Monday. The D-backs and Rockies have had the same result for five straight games.
Nonetheless, the Rockies, who began a stretch of 15 of 18 at home, won for the 12th time in their last 18 games. Monday was just their third victory in 11 homestand-opening games this season.
"I know I've felt we've had a chance all year, with the way our division has played," Rockies second baseman Clint Barmes said.
Monday's game was close to the end because the Rockies didn't do much offensively.
Giants starter Jonathan Sanchez (8-10) held them to three hits in seven innings. Two were Troy Tulowitzki's RBI triple followed by De La Rosa's RBI single. Willy Taveras walked once, had a hit and -- most of all -- stole three bases. The steals helped him score twice, on Garrett Atkins' sacrifice fly in the third and Giants reliever Keiichi Yabu's wild pitch in the eighth.
That stood mainly because of De La Rosa, who forced two double-play grounders and 12 ground-ball outs overall. He fanned four straight batters over the sixth and seventh innings.
On April 22, 2007, while with the Royals, he threw a career-high eight innings against the Twins but an unearned run scored. Monday marked the first time in his career that he left a game with as many as seven scoreless innings.
Earlier this season, he struck out 10 in a game and has fanned eight twice. As usual in his good games, he had an accurate fastball and used his slider to put hitters away, but his changeup worked as well as it has all season.
The only obstacle en route to the victory was Hurdle's decision to remove him for pinch-hitter Ian Stewart with two down and one on in the bottom of the seventh. Stewart struck out, and hearts began beating faster when Manuel Corpas gave up two hits to open the eighth.
"That's one of the ones that you lay yourself out there," Hurdle said.
De La Rosa has gone all-out for the Rockies since they acquired him, for a player to be named, from the Royals' Triple-A affiliate in Omaha on April 30.
He credits part of his success to a couple of behind-the-scenes personalities.
Vinny Castilla, a special front-office assistant, remains a clubhouse presence even though he retired as a player after the 2006 season. The two played together one winter in Mexico, and De La Rosa said that even during tough times this season, "he never let me go down." Also, talks with Ronn Svetich, a sports psychologist who holds the title of the Rockies' performance-enhancement coach, have helped.
After De La Rosa lasted just 1 2/3 innings in a road loss to the Marlins on July 31, the Rockies obtained right-hander Livan Hernandez from the Twins. Once Hernandez was ready, De La Rosa was dropped from the rotation.
But Aaron Cook's need for a break because of a back strain gave De La Rosa a chance to start on Aug. 15 at Washington. He struck out seven in six innings and won back his rotation spot. Since then, he has pounded the strike zone. Dazzling plays by alert defenders, like the ones third baseman Jeff Baker and shortstop Tulowitzki pulled off Monday, are not a coincidence.
"I'm not sure what it is," Tulowitzki said. "The only thing I know as a shortstop is he's throwing strikes."
Thomas Harding is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.