DENVER -- Rookie catcher Trevor Brown had a memorable game, and starter Jeff Samardzija recorded his first win for San Francisco on Tuesday night in the Giants' 7-2 victory over the Colorado Rockies.

Brown hit a pair of two-run homers to become the first Giants player whose first three hits of a season were home runs since Kevin Mitchell in 1991.

Hunter Pence added another two-run shot as the Giants continued their slugging ways. They extended a franchise record by homering in their first eight games to start a season. In that span, San Francisco has 17 homers, tied with Colorado for the major league lead.

Rockies wunderkind Trevor Story, who set a major league record with seven homers in his first six career games, went 0-for-4 with three strikeouts.

Samardzija, who signed a five-year, $90 million free agent contract with the Giants in the offseason, was effective in a 111-pitch effort. He allowed two runs and eight hits in eight innings, walking two and striking out five while recording nine ground-ball outs.

In his San Francisco debut April 6, Samardzija (1-0) allowed three runs on eight hits and three walks in 5 1/3 innings at Milwaukee in a no-decision.

"I was thinking maybe six, seven (innings), but I couldn't take him out," Giants manager Bruce Bochy said. "He just got better as he went."

After breaking up the Los Angeles Dodgers' no-hit bid with a home run in the eighth inning Friday night, Brown has matched his professional career high for home runs in five days. He hit three homers in 2013 for low Class A Augusta.

"If I was thinking about the entire season, I thought I might end with three," said Brown , whose multi-homer game was the first of his pro career. "Knock on wood, I still might end with three. I certainly didn't think my first three hits were going to be home runs."

Pence singled home a run in the third and hit a two-run homer in the fifth off Rockies starter Tyler Chatwood (1-1) that gave the Giants a 3-1 lead. Brown connected off Chatwood with two outs in the sixth to put the Giants ahead 5-2 and completed the scoring with another homer off Jason Gurka with two outs in the eighth.

"I made two pitches that hurt me," said Chatwood, who started for the second time since undergoing Tommy John surgery in July 2014. "The pitch that Pence hit out was what we wanted to do. It got to the spot, and he beat me to the spot. The other two-run homer with two outs -- I left the ball up and he hit out of the park. Other than that, I thought I did OK."

Samardzija gave up a run but minimized damage in the second when he allowed back-to-back singles to open the inning but got Nick Hundley to ground into a double play that brought home a run.

Nolan Arenado flared a run-scoring single to short left-center with two outs in the fifth, the ball eluding left fielder Angel Pagan. Carlos Gonzalez, whose single extended his hitting streak to a career-high 17 games dating to last season, tried to score from first, but Pagan threw him out at the plate.

Arenado's hit was the last off Samardzija, who retired the final nine batters he faced and retired the leadoff batter in six innings. For just the second time in his past 11 starts, Samardzija did not allow a home run. In five career games, two starts, at Coors Field, Samardzija is 1-0 with a 2.01 ERA.

"I think in a park like this, you need a sinker, and I throw it a lot," he said. "You just got to pitch off the barrel here. Nowadays, that's kind of a given anywhere you pitch, but especially here."

After retiring Story on a grounder in the first, Samardzija struck him out three consecutive times, finishing him off with a 96 mph sinker in the third, a 95 mph sinker in the fifth and a 91 mph cutter in the eighth.

"I was watching a lot of the stuff that he was hitting was middle and middle in," Brown said. "So we just tried to work him away, and if he was going to hit one out, hit it to the opposite side. I just kind of went with my best guess tonight."

NOTES: Giants C Buster Posey was held out of the game for precautionary reasons. He was available for use off the bench but didn't play. A foul tip off the bat of Dodgers 2B Chase Utley struck Posey in his right instep Sunday. ... Rockies RHP Jon Gray (abdominal strain) is scheduled to make his second rehab start on Friday for Class A Modesto and throw about 85 pitches. He felt fine after allowing two runs in 4 2/3 innings for Modesto on Saturday. If Gray comes through the next start without incident, he is expected to be ready to join the Colorado rotation. ... Rockies RHP Jason Motte (right shoulder strain) is pain-free, progressing with his strengthening exercises at the Rockies' complex in Scottsdale, Ariz., and will attempt to play catch in the next couple days. ... Rockies LHP Tyler Anderson (right oblique strain) and LHP Tyler Matzek (anxiety) threw bullpen sessions in Scottsdale, Ariz.