OAKLAND, Calif. -- Manager Don Wakamatsu stuck with Ian Snell even though the Seattle pitcher struggled to throw a strike or find a groove as his pitch count climbed.
The Mariners offense made things happen when Snell couldn't. The bullpen did its job, too.
Johjima's fourth-inning drive gave Seattle some breathing room after the A's had pulled within a run. Seattle went ahead 4-0 after the top of the first.
"Joh's home run was a big one to take that momentum back," Wakamatsu said. "That first inning trying to defend that four-run lead, I didn't think Snell was very good."
The Mariners provided Snell (4-1) with an early cushion he couldn't protect, but he hung tough and showed why the Mariners dealt for him right before the trading deadline.
"I got a little too relaxed," said Snell, who threw 107 pitches in five innings. "My ball was moving all over the place and I didn't feel like I could throw a strike. Wakamatsu left me in long enough to get a win. I gave my best. That's all I had in the tank tonight."
Ken Griffey Jr. returned to the Seattle lineup after missing six games with inflammation in his left knee. He went hitless in four at-bats with a strikeout and said before the game he is considering playing another season if it's the right move for both sides.
He said afterward his knee came through the game "fine."
The Mariners (71-64) matched a season high by moving seven games over .500, only the second time they've been there all year. Gutierrez also drove in a run in the ninth on a squeeze as Seattle beat the A's for the 13th time in 16 meetings.
David Aardsma pitched the ninth for his 34th save in 38 chances.
Seattle wasted no time jumping on Oakland starter Brett Tomko (3-3), who quickly fell behind against his former club.
Gutierrez hit a home run after Ichiro Suzuki's leadoff single in the first, then Hall connected four batters later following a two-out double by Adrian Beltre.
Kurt Suzuki had a two-run single in the bottom of the first for the A's, who scored an unearned run in the second but little else until Daric Barton's solo home run in the eighth. Oakland is coming off back-to-back winning series at home for only the third time this season.
"We just need to get one more big hit here or there to beat them," A's manager Bob Geren said. "Every game we've played them has been good, real close. It's just we fell short on most of them."
The Mariners won their third straight and are approaching the end of a grueling stretch -- this was game No. 30 in a run of 33 in 34 days. Seattle, which brought some momentum into the season's final month, started a 10-game road trip on the heels of a 7-3 homestand that began with a three-game sweep of the A's at Safeco Field from Aug. 24-26.
Tomko lost for the first time since being called up from Triple-A Sacramento on Aug. 17, allowing six runs on eight hits in 5 2/3 innings.
"I fell behind all three guys, and then when you're behind guys and don't make quality pitches and get too much of the plate, that's exactly what's going to happen," he said of the home runs.
Seattle is 10-3 against the A's and has won the season series for the second time in three years. The Mariners improved to 13-6 in California in 2009.
The Mariners were to take public transportation on the BART train to and from the games for the rest of the series with the Bay Bridge connecting San Francisco and Oakland closed for work all weekend.