SAN FRANCISCO -- Madison Bumgarner and Buster Posey were the winning battery for the San Francisco Giants on Monday night, but there'd have been nothing electric about the club's performance without their supporting cast.
Hunter Pence picked up Posey with a three-run home run in the first inning, and the three relievers who followed Bumgarner threw 3 1/3 near-perfect innings, a combination that made the difference in the Giants' 4-2 victory that ended the Colorado Rockies' five-game winning streak.
Santiago Casilla, Jeremy Affeldt and Sergio Romo provided the lifeline for a struggling Bumgarner, finishing off the left-hander's second win of the young season by retiring 10 of the final 11 Rockies. Ten of the 25 batters who faced Bumgarner reached base.
"That's nice to have," Bumgarner said of his bullpen. "A lot of teams don't have that."
The Rockies (5-2) hadn't lost since Opening Day, when they fell 5-4 in 10 innings to the Brewers in Milwaukee. Colorado had scored at least five runs in each of its five wins since then, including a total of 20 in its just-completed home sweep of the San Diego Padres.
The Rockies had their chances to score well more than two in the series opener in San Francisco, but they couldn't bust down the door on Bumgarner after he'd left it ajar on more than one occasion.
"We were trying to take him out of the game. He was throwing a lot of pitches," said Rockies slugger Carlos Gonzalez, who belted a solo homer off Bumgarner in the third inning but struck out with two on and two outs in the fifth. "That strikeout was a big out for him.
"Their games here, they're always trying to score first and then hold the opposition. That's what they did tonight."
The Giants (4-3), playing their first home night game of the season, were coming off successive daytime losses to the St. Louis Cardinals.
Even though Pence's two-out, three-run shot -- his third of the season -- in the first inning staked San Francisco to an early lead, Bumgarner (2-0) struggled through 5 2/3 innings. He allowed five hits and five walks (one intentional) but only two runs.
The Rockies knocked the left-hander from the game after 104 pitches, the last of which Chris Nelson grounded into left field for an RBI single that narrowed Colorado's deficit to 3-2.
With the potential tying run at second base, Casilla entered and struck out Yorvit Torrealba to retain the Giants' lead.
"I thought we had Bumgarner on the ropes a few times," Rockies manager Walt Weiss assessed. "He bent, but he didn't break. He made some good pitches."
Casilla stayed on to pitch a 1-2-3 seventh, and Affeldt was similarly flawless in the eighth. Romo yielded a booming double to Josh Rutledge to open the ninth -- the first baserunner he'd allowed this season -- before buckling down to record his fourth save in four tries. Romo struck out the next three batters.
The win improved Bumgarner's career record against the Rockies to 6-3, including 4-0 the past two seasons.
Colorado's Jorge De La Rosa (0-1) allowed only three more hits and no more runs through six innings after having surrendered three of each in the fateful first.
The Giants entered the game with just five hits in 30 at-bats with runners in scoring position, a .167 average that got even worse when Posey, following singles by Marco Scutaro and Pablo Sandoval, struck out with one out in the first.
But that became a distant memory one pitch later when Pence teed off on a low changeup over the middle of the plate and scorched it 20 rows up the left field bleachers for a 3-0 Giants lead.
"That was a mistake. It was supposed to be away," De La Rosa said. "That was the game right there."
Posey, who knocked in his first run of the season with an eighth-inning single to right, wasn't surprised to see Pence come through after the reigning National League Most Valuable Player hadn't.
"He's got some of the most power I've ever seen," Posey said. "I hit (batting practice) with him every day. I make sure I hit before him. I don't want to follow some of those moon shots."
De La Rosa admitted the strikeout on Posey played a role in Pence's home run.
"I lost a little concentration," he said. "Next time I have to be more focused."
NOTES: Gonzalez's home run in the third inning one-hopped into the San Francisco Bay. It only cut one run into the 3-0 Giants lead because, one pitch earlier, Eric Young Jr. was picked off first base by Bumgarner. ... Another of Bumgarner's biggest outs came one batter before the strikeout on Gonzalez in the fifth. Dexter Fowler, who set a Rockies record by recording at least one hit and one run in each of the team's first six games, just missed a three-run homer with a flyball that was caught on the warning track by left fielder Andres Torres. Fowler's streak ended on an 0-for-4 night. ... Colorado's Wilin Rosario, who tied a franchise record for a catcher by hitting three home runs in the season's first six games, was not in the starting lineup. He pinch-hit against Romo as the potential tying run with two outs in the ninth inning and was the closer's third strikeout victim. ... Few things are more of a sure thing in baseball than when Bumgarner gets three or more runs of offensive support. He's now 32-4 in such games. ... The Giants didn't score a first-inning run in their first six games. ... When Pagan grounded into a 1-6-3 double play in the fifth inning, it was the Giants' 10th of the young season, extending the club's league lead in that dubious category. ... The Rockies had a total of just 13 at-bats against left-handed pitchers in their first six games.