The injury-depleted Colorado Rockies try to build on an improbable victory when they visit the first-place San Francisco Giants on Saturday in the second contest of a three-game series. Colorado erased a two-run deficit by scoring five in the ninth inning of Friday's 7-4 win, but its third straight triumph came with a cost as Troy Tulowitzki - its best player - left with a right toe injury and staff ace Jorge De La Rosa departed after three innings because of lower back soreness. The Rockies are already without stars Carlos Gonzalez, Michael Cuddyer and Nolan Arenado, and two pitchers in the season-opening rotation - Tyler Chatwood and Brett Anderson.San Francisco, which leads the National League West by 7 1/2 games over Los Angeles and sits 10 1/2 on top of Colorado, has lost fourth of its last five games. Usually reliable closer Sergio Romo, who shares the major league lead with 20 saves, was charged with all five runs in the ninth Friday and has allowed nine in two innings covering his last three appearances against the Rockies. The Giants' Ryan Vogelsong is coming off his worst start of the season and opposes Christian Bergman, who lost his major-league debut Monday despite pitching well enough to win.TV: 4:05 p.m. ET, ROOT (Colorado), CSN Bay Area (San Francisco)PITCHING MATCHUP: Rockies RH Christian Bergman (0-1, 3.00 ERA) vs. Giants RH Ryan Vogelsong (4-3, 3.84)Bergman was one of three Colorado pitchers making his major-league debut in a six-day span when he allowed two runs and six hits in six innings of a 3-1 loss to Atlanta. "I was happy with the outing," the 26-year-old Californian told reporters. "It was a thrill, for sure. It's something I've wanted to do since I was 4 years old. So it was a thrill. I just wish we had won." Bergman was 4-4 with a 3.84 ERA in 12 starts over 75 innings with Triple-A Colorado Springs at the time of his call-up.Vogelsong allowed six runs and nine hits - including a career-high six extra-base hits - in six innings of a 9-2 loss to Washington on Monday. The 36-year-old North Carolina native was 3-0 with a 2.05 ERA and 27 strikeouts in 26 1/3 innings over his previous four turns. Vogelsong yielded five runs in 1 1/3 innings of an 8-2 loss in Colorado on April 21 to fall to 5-2 with a 3.90 ERA in 14 games against the Rockies - 3-0, 1.84 in six appearances outside Colorado.WALK-OFFS1. Rockies 1B Justin Morneau is 8-for-16 with eight RBIs in his last four games.2. Tulowitzki (17 homers, 43 RBIs) leads the majors in hitting (.356), on-base percentage (.449), slugging percentage (.662) and OPS (1.111).3. Colorado, which has won only four of its last 19 games at AT&T Park, is 58-116 all-time in San Francisco.PREDICTION: Giants 3, Rockies 2