Colorado @ San Francisco preview

Last Meeting ( Sep 18, 2012 ) Colorado 3, San Francisco 6

It is only a matter of time before the San Francisco Giants win their second National League West title in three years, and playing the Colorado Rockies is expediting the process. The Giants will try for their fifth straight victory over Colorado when they host the Rockies on Wednesday in the penultimate game of the four-game series. San Fransicso, which has a magic number of seven to clinch the West, is 12-4 against Colorado this season as it continues a 10-game homestand. San Francisco's Matt Cain will try for his career-high 15th victory and will oppose Colorado's Tyler Chatwood, who is 0-1 with an 8.49 ERA in three September starts.

The Rockies (58-89), who have lost 11 of their last 13 games overall and on the road, need to win nine of their last 15 games to avoid setting a club record for losses. They dropped 95 games in their inaugural 1993 season and again in 1995. A bright spot for Colorado has been the hitting of Wilin Rosario, who hit his major league rookie-leading 25th homer in Tuesday's 6-3 loss. He also tied Todd Helton's rookie club record set in 1998. Rosario, though, leads the major leagues with 20 passed balls, a Rockies record.

TV: 10:15 p.m. ET, Root Sports (Colorado), CS Bay Area (San Francisco)

PITCHING MATCHUP: Rockies RH Tyler Chatwood (4-4, 5.65 ERA) vs. Matt Cain (14-5, 2.93)

Chatwood allowed four runs and five hits in 3 2/3 innings but didn't take the loss in the Rockies' 7-4 setback at San Diego on Friday. Chatwood split a pair of decisions against the Giants on Aug. 5 and 10, pitching five shutout innings in a 3-0 victory at San Francisco after allowing three runs (one earned) and walking four in 3 1/3 innings in an 8-3 loss. His last win came Aug. 28, when he limited the Dodgers to two runs in five innings in an 8-4 victory. The Giants' roster is hitting .140 against Chatwood.

Cain, is 6-3 with a 2.26 ERA at home this season, including a perfect game. He is 14-7 with a 3.20 ERA in 27 starts against Colorado, including a 9-3 victory Aug. 11 when he yielded two runs and seven hits in 7 1/3 innings. Cain is 4-0 over his last seven starts and won at Arizona 6-2 on Friday, when he allowed one run and four hits in five innings but walked a season-high five. He recorded three straight no-decisions prior to Friday. The Rockies' roster is hitting .203 against Cain.

WALK-OFFS

1. San Francisco OF Xavier Nady went 2-for-3 with two RBIs on Tuesday. He was released by Washington in June and is 6-for-18 in seven games with the Giants since being called up from Triple-A Fresno.

2. The Giants' Buster Posey went 0-for-2 with two intentional walks Tuesday and saw his average drop to .333. He trails suspended teammate Melky Cabrera by 13 points and fellow MVP candidate Andrew McCutchen of the Pirates by six in the NL batting race.

3. Rockies LF Carlos Gonzalez (left hamstring) didn't play Tuesday. He left Sunday's 12-11 loss at San Diego after the top of the sixth and pinch hit Monday.