Jorge De La Rosa continues to build his case for the NL Cy Young Award.
De La Rosa (16-6, 3.31 ERA) may have a chance to become the NL's first 17-game winner and would become the second left-hander in franchise history to reach that plateau. He would join Jeff Francis, who won 17 in 2007.
Washington's Jordan Zimmermann also has 16 wins and pitches earlier Tuesday.
De La Rosa says he learned to be more effective watching tape while being out last year due to reconstructive surgery. He has also fought through a left thumb bruise that has been bothering him for the past couple of months.
"It's still sore, but I want to pitch," De La Rosa said. "It's not worse. It's not better. It's the same. It just needs rest to get better."
The Rockies are 11-4 when De La Rosa starts against San Francisco, and he's 8-4 with a 3.28 ERA in those outings. However, he is 1-1 with a 4.76 ERA in three matchups this year, and is also 0-3 with a 6.32 ERA in his last three starts at AT&T Park.
Pablo Sandoval is 5 for 9 off De La Rosa this year and Marco Scutaro is 4 for 8.
The Colorado franchise record for consecutive winning starts is seven, set by De La Rosa in 2009 and matched by Ubaldo Jimenez the next year.
The Rockies (66-79) fell to 0-4 on this nine game trip with Monday's 3-2, 10-inning defeat. They have totaled eight runs while batting .195 during this skid.
"We've struggled to score on the road this year and that's been the trend here,'' manager Walt Weiss said. "When you score two runs, like we've done a handful of times already on this team, that makes it tough to win games."
Brandon Belt's RBI single in the 10th gave San Francisco (65-79) its second straight walk-off win after Angel Pagan had an RBI single in the 11th in Sunday's 3-2 victory over Arizona.
"We want to finish the season on a positive note heading into next year,'' manager Bruce Bochy said. "It's all about playing better baseball. We're playing like the team that we are now. It's all about pride."
San Francisco will start Ryan Vogelsong (3-5, 5.62), who is 1-1 with a 3.57 ERA in six starts since returning Aug. 9 after missing nearly three months with a fractured right hand.
Vogelsong is 5-1 with a 2.40 ERA in seven starts against the Rockies, who he has not faced this year. He's 3-0 with a 0.64 ERA in four career home starts against them - games in which the teams have totaled 15 runs.
Colorado catcher Wilin Rosario could return after missing three straight games with problems with his wisdom teeth. Center fielder Dexter Fowler's status is not clear after he has missed three straight games with a knee injury.
Todd Helton got Monday off and figures to be back in Colorado's lineup a day later.