The game was tied 3-3 ahead of the 10th inning, however, runner Jack Lopez amassed a run on Tom Murphy's passed ball to kick off the scoring in the six-run inning. The Red Sox have now beaten the Mariners the second day in a row.
All three games in the series between playoff contenders were decided in the eighth inning or later. "It was playoff baseball," Red Sox manager Alex Cora said, according to Associated Press inputs. "It feels that way. It's fun, to be honest with you."
For the two wildcard spots, ahead of the game, the Red Sox, Toronto and New York Yankees were all level on points, while Seattle started the day three games behind the trio.
Meanwhile, at the start of the 10th inning, Alex Verdugo doubled against Eric Swanson (0-3), sending Lopez to third. Swanson hit Hunter Renfroe with a chest-high fastball on his first pitch, but the ball bounced over the top of Murphy's glove and into the backstop, bringing the score to 4-3.
Martinez made it 5-3 with an RBI single one out later.
For the Red Sox, Adam Ottavino (7-3) threw 1 1/3 innings to complete the eighth and ninth innings, getting his second win in as many days. He struck out two batters.
After three innings, the score was 3-3.
Bobby Dalbec of Boston advanced to third base in the eighth inning on a walk, a stolen base, and Jose Iglesias' single against reliever Casey Sadler. With two outs, Paul Sewald came in to retire pinch-hitter Verdugo on a popup, keeping Sadler's AL-leading 19 2/3-inning scoreless streak alive.
Jarred Kelenic hit a liner to right field that bounced a foot wide in the ninth inning, nearly ending the game in Seattle's favour.
Renfroe hit a solo home run in the first inning, and Kevin Plawecki and Jose Iglesias each drove in two runs in the second for a 3-0 lead over Mariners starter Marco Gonzales.
After the second inning, Gonzales retired 12 of 13 hitters, striking out seven and not allowing a single.
In the third inning, Seattle made a comeback. Kelenic and Murphy singled, Renfroe made a throwing error in right field, and Kyle Seager's two-run double knotted the game.
With inputs from the Associated Press