SEATTLE -- One of the things that Boston general manager Ben Cherington stressed when talking about the final month of the season Monday was that, wins and losses aside, his club was going to be competitive.

That really hadn't been the case during a seven-game losing streak, but Tuesday the Red Sox flexed their muscles after falling behind 3-0, the kind of competitive drive that Boston hadn’t shown at all on this West Coast trip.

Home runs by Cody Ross (three-run shot) and Ryan Lavarnway in the sixth inning gave the Sox the lead and they held on for a 4-3 win over the Mariners that brought their nasty slide to an end.

Seattle starter Blake Beavan was working on a shutout after five innings, but he never made it through the sixth. Singles by Dustin Pedroia (a 15-game hitting streak) and Jacoby Ellsbury set up Ross, who delivered his 20th homer, a three-run blast to left.

Two batters later, Lavarnway blasted his first homer, and just like that, the Red Sox had a 4-3 lead and Beavan had a quick exit.

Lefty Jon Lester, who was in constant trouble in the first five innings, kept the Red Sox in the game in the bottom of the fifth by striking out Justin Smoak and Miguel Olivo with two men on when a hit could have broken the game open.

Once he got the lead, Lester had his first clean inning of the game, then he turned it over to the Boston bullpen, which threw three shutout innings, with Andrew Bailey surviving a two-out triple in the ninth by Eric Thames for his second save of an injury-shortened season.

Breakthrough: Shortstop Jose Iglesias, who was looking for something, anything, to get him off the 0-for-16 that he brought into the game, finally got it in his second at-bat. His hitless streak ended when he chopped a grounder down the third-base line. It hopped over third baseman Kyle Seager's leap and kicked toward the outcropping of the left-field stands for a double.

Loney tunes: James Loney, who had only faced Beavan for one at-bat in his career, doubled to lead off the second inning and made it to third base with one out, only to be stranded. Undeterred, Loney singled with two out in the fourth, but nothing came of that either.

Homer (un)happy: Lester allowed back-to-back homers to Franklin Gutierrez and Seager in the third inning. It was the first time in six starts that Lester had allowed more than one homer. Even so, that pushed Lester’s homer total this season to 22, the most he's allowed in a season.

Ross the boss: This trip hadn’t been kind to Ross. He came into the game 4-for-23 (.174), then stretched that to 4-for-25 (.160) before turning things around with his three-run bomb in the sixth. He’d gone 10 games without a homer, but now has 20, the first time since 2009 that he’s reached that total.