OAKLAND, Calif. -- Oakland A's left fielder Khris Davis didn't hit his first home run last season until his 14th game, but he wound up with a career-high 42.

Davis hit two home runs in the Athletics' season-opening 4-2 victory against the Los Angeles Angels on Monday night at the Oakland Coliseum, and there is no telling how many he will have this year.

"I don't think there is a ceiling for a guy with his kind of power," said A's catcher Stephen Vogt, who also homered. "He's a smart hitter, too. He knows his swing really well, knows his approach. Hopefully it continues. It'll be fun to watch him."

Davis, who finished 3-for-4, gave no hint in a homerless spring training of what was to come Monday.

"Quiet? I throw (batting practice) to him almost every day, and I don't know if he hit a ball out in BP this year in spring training, let alone in a game," A's manager Bob Melvin said. "And then he hits two balls on a cold night that are no-doubters."

Davis wasn't worried.

"Takes me some time to get going," he said.

Mike Trout hit a two-run homer in the third inning and doubled in the eighth for the Angels.

Kendall Graveman, making his first career Opening Day start, allowed two runs on six hits for the A's, who won on Opening Day for just the second time in the past 13 seasons. He struck out seven and walked two.

Graveman (1-0) also escaped unscathed after giving up back-to-back singles to start the game. He got Trout to ground into a double play, then retired Albert Pujols on a ground ball.

"I felt comfortable," Graveman said. "I wasn't nervous. I was just ready to get out there. And then you start out base hit, base hit. I just had to step back, and I think that's where I've matured a lot. Just step back, step off the mound, 'Hey, I can get a ground ball here, get a double play and we're right back in the ballgame, we're right where we want to be.' I think in the past it probably would have escalated."

Davis broke a 2-2 tie in the sixth inning with a home run to left off Angels starter Ricky Nolasco (0-1). The right-hander hung a first-pitch curve, and Davis crushed it.

Davis led off the eighth with a home run to deep left-center off JC Ramirez, increasing Oakland's lead to 4-2.

Trout lined Graveman's cutter over the left-field wall with two outs in the third after Kole Calhoun walked.

"Put a good swing on it," Trout said of his homer. "Couple good at-bats tonight. You get into the season, you get so anxious, you want to do so good. Keeping it simple helps you calm yourself. Once I got in the box the first at-bat, I just tried to calm myself down.

"Good crowd tonight. It's not a good feeling when you don't win, but we'll come get them tomorrow."

Nolasco gave up three runs on seven hits over 5 2/3 innings in his fourth career Opening Day start and first with the Angels. He struck out four and walked two.

"I just made a couple of mistakes there to Vogt and Davis, kind of cost us the game," Nolasco said. "But I felt good."

A's right-hander Ryan Dull struck out the side in the seventh. Left-hander Sean Doolittle retired both batters he faced in the eighth. Ryan Madson gave up a double to Trout, but after Pujols was issued an intentional walk, C.J. Cron grounded into a force out.

Right-hander Santiago Casilla pitched a scoreless ninth for the save.

NOTES: The A's named their field at the Oakland Coliseum "Rickey Henderson Field" and honored the Hall of Fame outfielder and native of Oakland in a pregame ceremony. "It's a great honor," Henderson said. "Growing up in Oakland as a kid, playing in the parks around the ballpark, I had no idea this chance would ever come. The first thing was me getting an opportunity to play for the Oakland A's and being from Oakland, and now this has happened. So this is just a special moment." ... Albert Pujols, who underwent offseason foot surgery, served as the Angels' designated hitter and went 0-for-3 with a walk. He won't play in the field this series. ... 3B Trevor Plouffe went 1-for-3 with a walk in his A's debut.