What looked like a high-scoring affair after an inning turned into a pitchers' duel.

Colorado starter Antonio Senzatela settled down after a shaky first inning, and DJ LeMahieu's run-scoring single in the second inning provided the winning margin as the Rockies beat the San Francisco Giants 4-3 on drizzly Sunday afternoon at AT&T Park in San Francisco.

After Colorado scored three times in the top of the first inning, the Giants tied it in the bottom half of the inning.

In the second, Tony Wolters singled, moved up two bases on a sacrifice and a groundout, then scored on LeMahieu's single to center to put the Rockies ahead for good.

It was 4-3 after an inning and a half, but then the pitchers took over.

Senzatela (2-0) allowed three runs on seven hits in seven innings. He held San Francisco batters to just four hits after the first inning.

"I woke up and said, 'OK, I need to make an adjustment and keep the game close for my team,'" Senzatela told the Denver Post.

The rookie retired nine in a row in innings 2 through 4, going to his fastball almost 80 percent of the time.

"That is the thing our minor league people were crazy about: His ability to move the fastball, to pitch in to both left and right-handed hitters, throw the ball down and away to both, to elevate when needed," Rockies manager Bud Black told the Post.

"What he's doing is pitching fundamentally sound. And he's pitching his game. As pitchers move on, and they get multiple weapons, they'll pitch to a hitter's weakness. Right now, he's primarily pitching to his strengths."

Giants starter Jeff Samardzija (0-3), who gave up hits to the first four Rockies he faced, allowed just two hits after the second inning. Samardzija had eight strikeouts and issued no walks in seven innings.

"We're playing good ball right now," Samardzija told the San Francisco Chronicle. "We're down a couple of guys, but it's Giants baseball. We're going to keep going out there playing hard and go after every game."

LeMahieu was 2-for-4 and scored a run, and Nolan Arenado was 2-for-4 with two RBIs for Colorado.

"The games are always tough here," LeMahieu told the Post. "But we have a lot of guys who like playing in environments like this. These are dogfights. But we really rise to the occasion."

San Francisco first baseman Brandon Belt was 2-for-4 with a run, his first multi-hit game in more than a week.

Rockies closer Greg Holland pitched a 1-2-3 ninth for his major-league-leading seventh save this season. Holland has yet to allow a run in seven appearances.

Neither bullpen gave up a hit or walk in six combined innings.

The Rockies got to Samardzija early, scoring three times before recording an out.

Charlie Blackmon led off the game with a home run over the center field wall. LeMahieu singled, and Carlos Gonzalez doubled. LeMahieu and Gonzalez both scored on a double by Arenado.

"We've played a lot of close games," Samardzija said. "I think we need to find a way to scratch one or two across here when we need it to close the gap and stay away from the heart of the other team's bullpen. That comes with not letting runs in early, taking a lead and taking it late into the games."

In the bottom of the first, leadoff man Denard Span doubled, Belt singled, and Span scored on a Hunter Pence sacrifice fly. Brandon Crawford tripled to score Belt, and Crawford scored on a sacrifice fly by Nick Hundley.

Colorado won a four-game series in San Francisco for the first time ever, taking three of four.

"This is a tough place to play, no doubt about it," Black said. "I can sense our guys like coming here. This park has energy. We played hard and gritty all the way through."

Colorado will be in Los Angeles on Tuesday to take on the Dodgers. The Giants are off Monday before welcoming Kansas City for a two-game series beginning Tuesday.

NOTES: Colorado 3B Nolan Arenado appears to be over last week's mini-slump. Arenado, who was 2-for-13 over a four-game stretch, followed Saturday's three-hit effort by going 2-for-4 Sunday. ... Giants LF Jarrett Parker (broken right collarbone) was placed on the 10-day disabled list. San Francisco recalled LHP Steven Okert from Triple-A Sacramento, and he retired the only batter he faced Sunday. ... Giants All-Star C Buster Posey (concussion) is expected to come of the disabled list on Tuesday. San Francisco manager Bruce Bochy said Posey likely would be the designated hitter during a two-game series Tuesday and Wednesday in Kansas City. "When he gets back in there, it definitely changes things," 1B Brandon Belt said of Posey. "I can definitely say with a lot of confidence that it gives us more confidence with him in there."