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An illness to Troy Tulowitzki and an injury to Aaron Cook may be poorly timed as the Colorado Rockies hold a slight lead in the tightening NL wild-card chase. Having Jorge De La Rosa take the mound could help them create some breathing room on the surging San Francisco Giants.

De La Rosa looks to continue his hot stretch Saturday night when the Rockies host the Giants in the second of this key four-game series.

The Rockies (68-54) might be without Tulowitzki for a second consecutive game after a stomach flu ruled the shortstop out of Friday's 6-3 loss to the Giants (67-55). Colorado also lost Cook, who exited the loss in the fourth inning because of a sore right shoulder as the team's wild-card lead dwindled to one game over San Francisco.

Rockies manager Jim Tracy said Tulowitzki vomited earlier Friday and was told to stay home rather than report to Coors Field with the rest of the team.

Tracy said he believes it's just a 24-hour bug but said the team will monitor the All-Star shortstop, who is hitting .274 with a team-leading 23 homers and 66 RBIs.

"When we revisit it, if it's tomorrow or if it's the day after, we have to make sure that he's completely hydrated and not run the risk that he is a little bit dehydrated and he ends up pulling a hamstring or something like that," Tracy said.

With Tulowitzki potentially out again, the Rockies could use another strong performance from De La Rosa (11-8, 4.58).

The left-hander has done his part to boost their playoff chances, going 9-1 with a 3.27 ERA and 64 strikeouts in 66 innings over his last 11 games -- 10 starts -- en route to a career high in victories. That stretch includes a 6-0 record and 2.72 ERA in seven games -- six starts -- in Denver, where the Rockies are 32-24 and will play 17 of their next 20.

De La Rosa labored through 5 2/3 innings Sunday, throwing 112 pitches but allowing only one unearned run with nine strikeouts in a 7-3 win at Florida to help Colorado avoid a doubleheader sweep. That performance came six days after he allowed one run while fanning 11 in 7 2/3 innings of an 11-5 win over Chicago.

De La Rosa has been outstanding against the Giants, posting a 4-0 record with a 2.36 ERA in eight games -- five starts. He's won his last four starts against them while posting a 0.99 ERA. He beat the NL West rivals again July 25, yielding two runs with seven strikeouts in 7 1/3 innings of an 8-2 victory at home.

San Francisco has a chance Saturday to pull into a tie with Colorado for the wild-card lead for the first time since Aug. 9.

"It's big for us," manager Bruce Bochy said.

The Giants have won four of five, compiling a .319 batting average in that span while outscoring opponents 26-11.

Aaron Rowand has been a big part of the surge, hitting .550 with two homers and five RBIs. The center fielder, though, is 2 for 15 lifetime against De La Rosa.

San Francisco rookie Joe Martinez (3-1, 4.76) will get his first start against Colorado, seeking to build on his 2-1 mark and 4.40 ERA in three starts since returning from the disabled list Aug. 5.

The right-hander, who went on the DL with a concussion after being hit by a line drive April 9, allowed one run in five innings of a 10-1 win at New York on Monday.