OAKLAND, Calif. -- What shaped up as a likely pitcher's duel between Felix Hernandez and Kendall Graveman turned into a 14-3 rout for the red-hot Seattle Mariners against the Oakland A's on Saturday at the Oakland Coliseum.

Hernandez pitched six shutout innings and Nelson Cruz went 3-for-4 with two doubles and three RBIs as Seattle continued its playoff push.

The Mariners, who entered the game trailing Detroit and Baltimore by 3 1/2 games for the American League's second wild-card spot, won for the fourth straight time.

"I think everybody is aware of what's going on," Cruz said. "We've been focusing on one game at a time and just going out there and giving our best every day."

Hernandez (11-5) improved to 23-8 for his career against Oakland and 12-3 at the Coliseum. He tied Tommy John for the most wins at the Coliseum by a visiting pitcher.

Hernandez was coming off of back-to-back rough starts against the Texas Rangers, but he held the A's to six hits and didn't let a runner get past second. Hernandez, who permitted a combined eight walks in his previous two starts, yielded one free pass and struck out two.

"First two innings I was a little wild," Hernandez said. "The ball was moving all over the place, sinking and cutting. After that it was something (catcher Jesus Sucre) and I decided, just find the strike zone and throw our fastball."

Graveman (10-10) allowed career highs in earned runs (eight) and hits (12) over five innings. Graveman had gone 9-3 with a 3.18 ERA in his previous 18 starts, but he fell to 0-3 this season against Seattle.

"I didn't locate," Graveman said. "Pitches away, the sinker away was running back over the middle, and the ones that I was trying to throw away to lefties were running off the plate, and they were taking good pitches. So overall just something all comes down to being able to locate.

"It's always disappointing no matter how good of a run or how bad of a run you've been on. To have and outing like that is disappointing, but you know what, I've learned in the past that you can't dwell on this. You've got to put it in the past and continue to work."

Cruz, who scored twice, had all three of his hits against Graveman. For his career versus Graveman, Cruz is batting .667 (10-for-15) with one home run, two doubles and four RBIs.

Norichika Aoki also had a big day at the plate for the Mariners, going 3-for-5 with two doubles, driving in two and scoring three runs. Kyle Seager hit his 28th home run of the season, a solo shot leading off a six-run seventh inning. He had two of Seattle's 17 hits and drove in two.

"Outstanding offensive day against a guy who's been throwing the ball pretty well," Mariners manager Scott Servais said. "Obviously we'd seen him a couple times early this year. Our guys, their timing is good, their rhythm is good in the batter's box, we're having a lot of good at-bats.

"It's up and down the lineup, not just one or two guys carrying us, which is great to see. Plenty of run support for Felix today. Not his sharpest, but he got on a nice roll there and kept them off balance."

Rookie Ryon Healy went 3-for-4 with a two-run homer in the eighth inning for the A's. The home run was his eighth of the season. Bruce Maxwell, another rookie, had two hits one day after his career-high three-hit game against the Mariners.

"He's been here long enough to where teams are making adjustments to him and he's continuing to make the adjustments himself," A's manager Bob Melvin said of Healy. "He is certainly a guy we are looking for next year to be an important factor and play a lot."

The Mariners, who have won 11 of their past 12 games in Oakland, took control early, scoring twice in the first inning and four times in the third to build a 6-0 lead.

Aoki led off the game with an opposite-field double down the left field line, moved to third on Seth Smith's infield single and scored when Robinson Cano grounded into a double play. Cruz doubled off the center field fence, and Seager lined an RBI single to right.

In the third, Aoki had a leadoff walk, Smith singled and Cano walked, loading the bases. Cruz doubled off the left field wall, driving in Aoki and Smith. With one out, Graveman intentionally walked Adam Lind, reloading the bases. But Sucre brought Cano home with an infield single. Then Cruz scored on Ben Gamel's fielder's choice ground ball.

Seattle extended its lead to 8-0 in the sixth. After Gamel and Ketel Marte opened the frame with back-to-back singles, Aoki brought them home with a double to left-center.

"No one in here has given up," Aoki said. "We just got to fight until the end, just keep going."

NOTES: Mariners CF Leonys Martin was out of the starting lineup Saturday, getting a day off. He went 0-for-4 with two strikeouts on Friday night against Oakland. "Leonys needs a day," Seattle manager Scott Servais said before the game. Ben Gamel started in center field for the first time this season. ... The Mariners activated RHP Tom Wilhelmsen (lower back spasms) from the 15-day disabled list before Saturday's game. The reliever had been on the DL since Aug. 27. ... A's LHP Sean Manaea (strained upper back) threw a 55-pitch bullpen session Saturday and, barring a setback, is expected to rejoin the rotation on Wednesday at Kansas City. The A's will have a six-man rotation once Manaea returns. ... A's rookie RHP Jharel Cotton will make his second career start on Tuesday against the Royals. ... A's RHP Sonny Gray (strained right forearm) will play long toss again Sunday and might throw a few pitches off the mound for the first time since going on the disabled list Aug. 7.