OAKLAND, Calif. -- The Seattle Mariners' bullpen was a huge question mark when the season began. Now it is unquestionably one of the team's biggest strengths.

Relievers Vidal Nuno, Nick Vincent, Joel Peralta and Steve Cishek combined to blank the Oakland A's on no hits over the final three innings, and the Mariners withstood a two-homer game by Khris Davis to hold on for a 4-3 victory at the Oakland Coliseum on Monday night.

Seattle's bullpen has allowed nine runs over its past 48 innings over 17 games, good for a 1.69 ERA in that span.

"Our bullpen's been outstanding," Mariners manager Scott Servais said. "They really have since the Opening Day. I know it was a question mark on our team coming into the season, but we've had some guys step up, kind of having bounce-back years, which is what you need out of a bullpen with a couple injuries we've had.

"But really excited and really confident in our guys down there, and they've got some confidence going as well."

Cishek pitched a scoreless ninth for his seventh save in seven chances, but the A's made him sweat.

After retiring the first two batters he faced, Cishek struck out catcher Stephen Vogt for what would have been the third out, but Vogt reached base on a wild pitch. Pinch runner Tyler Ladendorf stole second and Chris Coghlan walked, but Cishek struck out pinch hitter Jed Lowrie to end the game.

"We've got a bunch of competitors out there," Vincent said. "A bunch of guys grinding to get outs. Not one person has a role besides Cishek, so everybody's just ready from the sixth inning on. And I think the biggest thing is we go in there and throw strikes when you try to stop that fire that's getting lit right then for the starters."

Robinson Cano and Nelson Cruz each had three hits for the Mariners. Cano went 3-for-4 and scored twice, raising his batting average from .237 to .257. Norichika Aoki went 2-for-4 with a double, a stolen base and a run. Kyle Seager had an RBI double.

Davis hit a solo home run in the second inning and a two-run shot in the seventh. After an ice-cold start for his new team this season, the former Milwaukee Brewers outfielder now has five home runs, all in the past 13 games.

"He's got such great power," Vogt said of Davis. "He's going to be big for us in the middle of the order all year. He got his pitch twice and didn't miss it. It's fun to watch him hit the ball a long way."

Mariners right-hander Nathan Karns (3-1) allowed three runs on six hits over six innings. He struck out five, walked one and allowed both of Davis' home runs.

"I kind of had something to make up for from the first game against these guys so I just wanted to go out there and work ahead, learn from my mistakes," said Karns, who gave up four runs over five inning in a 6-1 loss to Oakland in his first start of the season.

"You got to give props to Davis. He's swinging a good bat right now. The scouting report says don't groove a curveball in there, and I did that twice. So kudos to him."

A's right-hander Kendall Graveman (1-3) yielded four runs over 6 1/3 innings. He gave up 10 hits, matching his career high set in his previous start when he allowed six runs and a career-high-tying three home runs over 4 2/3 innings in a 7-3 loss to Detroit.

Graveman struck out six and walked one.

"He kept us in the game," A's manager Bob Melvin said of Graveman. "We scored a couple runs to get back in it, but it is a difficult lineup with all the lefties they have.

Vogt went 3-for-4 with a double.

The Mariners snapped a 1-1 tie with two runs in the sixth inning off Graveman.

Cano led off with a single and went to second when Cruz grounded a single to right. Graveman got Adam Lind to ground into a double play, but Seager lined a double into the right field corner, driving in Cano. Chris Iannetta followed with an RBI single.

The Mariners extended their lead to 4-1 in the seventh. Aoki lined an opposite-field double to left, stole third and raced home when Vogt's throw went into left field for an error.

The A's scored two runs in the bottom of the seventh. Josh Reddick lined a leadoff single, and Davis crushed Karns' first-pitch curve over the center field wall. Vogt doubled down the right field line, ending Karns' night, but Seattle's bullpen blanked Oakland the rest of the way.

NOTES: Oakland INF/OF Mark Canha started at third base for the first time in his major league career. He made two substitute appearances at third this season and one last season. ... A's 2B Jed Lowrie was out of the starting lineup to rest a sore calf but pinch hit in the ninth and struck out. ... Mariners RHP Joaquin Benoit (right shoulder inflammation) played catch in the outfield Sunday and is "moving in the right direction" in his recovery, manager Scott Servais said. Benoit went on the 15-day disabled list April 25, retroactive to April 22. ... Mariners LHP Charlie Furbush (left shoulder biceps tendinitis) threw 10 to 12 pitches off a mound Sunday and "felt great," Servais said.