PHOENIX -- San Francisco Giants left-hander Madison Bumgarner began the 2015 season like he ended last season -- looking dominant.

Bumgarner allowed one run on six hits with three strikeouts in seven innings in the Giants' 5-4 Opening Day victory over the host Arizona Diamondbacks at Chase Field on Monday.

San Francisco erupted for four runs in the fifth inning off Arizona starter Josh Collmenter to give its ace more than enough run support, which it would need as Arizona made a late run in the eighth.

"I felt pretty good," Bumgarner said. "I was making pitches and getting ahead of hitters. The defense picked me up multiple times. It was an all-around team effort. We played the kind of baseball we need to play to win."

Five of the six hits Bumgarner allowed were singles as Arizona struggled to hit any of his offerings hard. Mark Trumbo was the only Diamondback who tagged Bumgarner as the slugger hit a towering RBI triple to center field that hit the wall just below the home run stripe more than 400 feet away.

Other that that, the left-hander did what he does best -- mixing pitches and keeping hitters guessing.

"I don't know what else we can say about him. He's special," Giants manager Bruce Bochy said of Bumgarner. "He goes out there, the first game of the season and throws a terrific game.

"He gave us what we needed and went deep into the game against a tough lineup."

This outing was the first step in adding another layer to the coming-out story Bumgarner wrote last postseason. Monday's outing is also an impressive starting point toward an encore performance that saw the 25-year-old emerge as the ace he was projected to become when he posted career highs in numerous categories in 2014 and the second lowest ERA of his career.

"I'm not worried about what happened six months ago, three months ago or last week," Bumgarner said. "I work to get better for the next day. That's how I like to go about my business."

Bumgarner made his second career Opening Day start Monday and continued his run of success in Arizona, as he is now 3-0 with a 1.46 ERA (6 ER in 37.0 IP) in his last six starts at Chase Field.

Matt Cain note: Bochy said he didn't have an update on Cain, who underwent an MRI for tightness in his forearm but was going to meet with general manager Brian Sabean and others for additional information.