Winning with Tyson Ross on the mound could be more difficult.The unlucky Ross has lost both starts this year to the Rockies, and the Padres have given him little support in losing his last four outings heading into Saturday night's matchup at Petco Park.San Diego (63-77) improved to 5-12 against Colorado by rallying for a 4-3 victory Friday. Chase Headley hit a tying homer to lead off the bottom of the ninth and pinch-hitter Jesus Guzman later singled with the bases loaded."I think that game was Chase Headley," Guzman said. "He win the game because he changed the game. If he don't change the game, I don't hit it."Ross (3-7, 2.99 ERA) went 0-1 with a 4.82 ERA in two April starts versus the Rockies and has also allowed one run over 3 1/3 innings spanning two relief appearances against them.The right-hander is 3-3 with a 2.45 ERA in eight starts since being re-inserted into the rotation July 23 at Milwaukee, but the Padres have totaled 14 runs of support for him in that span.San Diego has scored one run in each of Ross' last four starts, as he has gone 0-2 with a 3.70 ERA.Ross yielded one run over five innings and did not get a decision Sunday in a 2-1 loss to the Dodgers. He struck out a career-high 10 in a 105-pitch effort."I was just trying to execute in a couple of tough situations," Ross said. "Giving up one run and keeping us in the ballgame is always my goal."Troy Tulowitzki, Michael Cuddyer and Dexter Fowler are the only Rockies with two hits apiece against Ross.Fowler's status, however, is unclear after he left Friday in the sixth inning when he aggravated a left knee injury. The center fielder appeared to hurt the knee when he stole second base in the fifth.Cuddyer went 0 for 3 as his average fell to .329, dropping behind Atlanta third baseman Chris Johnson's .330 mark in the race for the NL batting title.Colorado (66-76) could have third baseman Nolan Arenado back in the lineup Saturday. Arenado, who leads all rookies with 117 hits, did not start Friday due to a thumb bruise, but entered to play defense in the ninth inning."I want to finish strong, and I want to play in every game after today," he told the Rockies' official website.The Rockies will start Tyler Chatwood (7-4, 3.29), who returned after missing a month with right elbow inflammation and left Sunday's 7-4 victory over Cincinnati after two-plus innings with a bruised right thumb."It's frustrating," he said. "You wait a month to start and that happens."The right-hander, 1-0 with a 5.23 ERA in two career starts against San Diego, had no setbacks Wednesday in a bullpen session.Headley is 3 for 6 off Chatwood and 8 for 24 during a seven-game hitting streak, although he is batting .171 in the season series.