Felix Hernandez fired his first shutout of the season and John Jaso plated the game-winning run in the ninth as the Mariners downed the Red Sox, 1-0, in the opener of a four-game series at Safeco Field.
Casper Wells registered the first extra-base hit of the game with a one-out double in the bottom of the ninth before Justin Smoak was intentionally walked by Scott Atchison (2-1).
Jaso entered as a pinch-hitter and laced a single to right fielder Cody Ross, who fired home as Wells rounded third base.
The throw was on line, but catcher Jarrod Saltalamacchia was unable to corral the short hop and Wells slid in safely to give the Mariners their second win in their last three games.
"(Atchison) just left it over the plate a little bit too much," said Jaso. "I'm glad I went up there in swing mode, not really looking to see a lot of pitches."
Hernandez (6-5) matched a career-high with 13 strikeouts and allowed just five hits and one walk.
"His stuff was moving all over the place," said Boston second baseman Dustin Pedroia of Hernandez. "He kept the ball out of the middle of the plate. He was pretty special tonight."
Red Sox starter Franklin Morales spun seven innings of three-hit ball with two walks and seven strikeouts.
Boston's best opportunity to score came in the top of the ninth. David Ortiz scorched a one-out single back up the middle before Hernandez issued his first walk of the night to Saltalamacchia, who battled back from an 0-2 count to earn a free pass.
Adrian Gonzalez then belted the ninth pitch of his at-bat deep into left- center field, but Michael Saunders chased it down and Will Middlebrooks flied out weakly to second base to end the threat.
The Mariners didn't move a runner into scoring position until the seventh, but they left the runner stranded 90 feet away as Brendan Ryan grounded out weakly to third to end the frame.
Hernandez has struck out 10-plus batters in each of his last two games. He struck out every Boston hitter at least once except for shortstop Mike Aviles...Seattle outfielder Franklin Gutierrez left the game in the bottom of the fourth when he was hit in the head by an errant pickoff attempt from Morales...Gonzalez extended his hit-streak to nine games...Boston swept a two- game set from the M's earlier in the year at Fenway.