Ryan Vogelsong hasn't been nearly that effective against them on the mound.Posey and Pence look to continue their offensive barrage as the San Francisco Giants attempt to conclude this three-game set Wednesday with back-to-back wins.Posey is hitting .481 with six homers and 18 RBIs in 12 games, and 13 of his 26 hits have gone for extra bases. He connected for a solo shot while driving in three more runs with a pair of doubles in Tuesday's 12-7 win at Colorado."He's on fire right now and looking really good," said George Kontos, who was credited with Tuesday's win. "Buster is a guy if something is not going right for him for a week or two or however long it is, he's a guy who's going to come out of it."He's going to get in his groove and do what we're all accustomed to seeing him do."Pence is on his own tear, getting two hits and one RBI on Tuesday to extend his hitting streak to 15 games, the longest by a Giant this year. The right fielder has a .393 average with 15 RBIs and 17 runs over that stretch, which seems likely to continue since he's batting .446 with five homers during a 15-game hitting streak against Colorado (55-84).Posey, who is 6 for 10 in this series, has a .382 career average against the Rockies and a .406 mark at Coors Field -- his highest at any visiting park with at least 39 at-bats.San Francisco (76-63), the NL wild-card leader, may need another brilliant offensive display with Ryan Vogelsong (8-9, 3.73) taking the mound. He's 2-2 with a 7.50 ERA in four lifetime starts at Coors Field and was hammered for five runs and three homers before being pulled with one out in the second of an 8-2 loss April 21.Vogelsong, though, enters this meeting 3-1 with a 2.58 ERA in six starts after earning a 13-2 win over Milwaukee on Friday. The right-hander allowed two runs with seven strikeouts in seven innings.He's been backed with 19 runs over his last two outings after getting an average of 1.81 in the previous eight."I'll take 13 all the time," Vogelsong said.The Rockies are struggling in nearly every facet during a 2-6 stretch, batting .198 while compiling a 5.59 ERA -- 7.48 from the bullpen.Drew Stubbs is doing his part, at least at home. The center fielder is hitting .364 at home compared to a .209 on the road, and that trend has continued of late. Stubbs' three hits in this series is one more than his total in 18 at-bats over his previous five games -- all on the road.Colorado is turning to rookie Christian Bergman (1-2, 5.74), who carried a no-hitter into the fifth inning Friday before allowing a double to Arizona starter Josh Collmenter. The right-hander left with one out in the sixth after allowing one run and two hits with a season-high five walks and did not figure in the decision of a 5-2 loss.Bergman didn't get a decision in his only meeting with the Giants on June 14, allowing three runs -- all on homers by Posey and Pence -- in six innings of a 5-4 win.