SAN FRANCISCO -- The San Francisco Giants get a chance to play the role of spoiler against the Colorado Rockies for the second straight September when the National League West clubs open a three-game series on Friday night.

Giants right-hander Chris Stratton (9-9, 4.99 ERA), bombed in back-to-back starts against the Rockies earlier this season, and Rockies left-hander Tyler Anderson (6-8, 4.89), winless in his last 11 starts, draw the starting assignments in the opener.

The Rockies (81-65) begin a nine-game trip in first place in the NL West, having moved a healthy 4 1/2 games up on third-place Arizona (77-70) with a 10-3 shellacking of the Diamondbacks Thursday at Colorado to complete a 3-1 series win.

The Los Angeles Dodgers (80-67) are in second place, 1 1/2 games behind the Rockies.

The Rockies will visit Los Angeles and Arizona for three games apiece next week to complete its road -- and NL West -- schedule. Colorado finishes the season at home against Philadelphia and Washington.

The Rockies found themselves battling the Diamondbacks, Cardinals and Milwaukee Brewers in mid-September last season when they went into San Francisco and lost two straight to a Giants team well out of contention.

Colorado then had to scramble just to claim the second wild-card spot in the NL by one game.

This year's San Francisco club finds itself in the same situation, having lost a West Coast era-record 11 straight.

Stratton has started two of those games and pitched pretty well in 4-1 and 4-3 losses to the New York Mets and Milwaukee Brewers, respectably. He allowed just seven hits in 11 innings in those games.

That was a marked improvement over the 13 runs and 19 hits he gave up in 9-8 and 8-1 losses in a home-and-home sequence with the Rockies bridging June and July.

Nolan Arenado homered in both of the games. The star third baseman hasn't been the only Colorado player who has rocked the 28-year-old Stratton in the past. Ian Desmond (.625), Trevor Story (.556), Charlie Blackmon (.500), DJ LeMahieu (.500) and Gerardo Parra (.500) all have .500 or better career batting averages against Stratton.

He has gone 1-1 with a 7.89 ERA in five games, including four starts, in his career against Colorado.

Anderson will face a Giants team that has hit even worse than he has pitched of late.

The 28-year-old hasn't won since July 4 and now leads the NL in home runs allowed with 29.

He was taken deep by the Giants' Gorkys Hernandez in a 9-8 Rockies home win on Sept. 3. Anderson did not get the win, pulled after 5 1/3 innings having allowed three runs and six hits.

Anderson has made six starts in his career against the Giants and went 1-2 with a 4.25 ERA.

Hernandez has two career homers against him in 10 career at-bats.

The Giants enter the series having scored one run in five straight home games. They've totaled just nine home runs (none in the last three outings) during their 0-for-September run of 11 games.