Scutaro has played in pain at various times over the last five months, his latest problem an inflamed rotator cuff that keeps him from extending his arm back to make the long throws often necessary playing shortstop. He copes with extra stretching, medication, and mounds of ice.

But Scutaro hits leadoff game after game, taking over the role vacated by Jacoby Ellsbury and helping spark an offense that is second in the majors in runs scored.

“You pretty much get the same player every day,’’ manager Terry Francona said. “I mean that in a good way. That’s a compliment.’’

Scutaro’s value was never more apparent than last night. He drove in four runs as the Red Sox danced around the raindrops to beat the Seattle Mariners, 6-3.

John Lackey pitched eight strong innings and struck out 10 as the Red Sox won their third straight and closed to within 5 1/2 games of the first-place Yankees in the American League East.

The Sox have two games remaining with the Mariners before playing a pivotal three-game series at Tampa Bay starting Friday. The Rays lead the Sox by 5 1/2 games in the wild-card race.

“We’re trying to hang in there and we’ve done a good job,’’ Scutaro said. “This team isn’t giving up.’’

Or as Mike Cameron said, “The white flag is not up. It’s yellow now. Be cautious of the Red Sox.’’

With the Sox down, 1-0, in the fifth inning against a better-than-expected Doug Fister, Scutaro came to the plate with bases loaded and grounded a single into right field. Adrian Beltre scored and Jed Lowrie raced around from second, just beating the strong throw of Ichiro Suzuki.

Scutaro is 6 of 11 with 16 RBIs in 13 plate appearances with the bases loaded this season.

After the Mariners rallied in the sixth to tie it, 3-3, Scutaro added a two-run single in the seventh inning, giving Lackey breathing room.

Lowrie and Daniel Nava led off with singles and moved up when Ryan Kalish put down a bunt. Righthander Sean White replaced Fister (4-9) and threw Scutaro the exact pitch he was looking for: a two-seam fastball a little up in the strike zone.

He lined it into center field for two more RBIs. A single by J.D. Drew and a sacrifice fly from Victor Martinez accounted for another run.

“With Ells being down he’s been unbelievable for us this year,’’ Lackey said of Scutaro. “He’s stepped up and really given us a presence in the leadoff position.’’

Scutaro is hitting a modest .276 with a .337 on-base percentage that is only a few percentage points above the league average. But his reliability is treasured, especially at a position that has been in flux for several seasons.

“He’s given us stability all year. He’s played through a lot and we all know that,’’ Francona said. “He’s showed up every day. We were really excited when we got him and we still are.’’

This latest injury is troublesome from a defensive standpoint. But Scutaro has not been affected at the plate. He is 15 of 39 in the last 10 games with eight runs and seven RBIs.

“Injuries, they’re going to come,’’ Scutaro said. “Sometimes you have no control over that kind of stuff. You prepare all offseason and then you show up to the ballpark every day and you do your work.’’

Lackey (12-7) had a rocky sixth, allowing two runs on three hits and his own fielding error. But he handled the Mariners with ease otherwise, allowing two earned runs with two walks.

The 10 strikeouts were the most for Lackey since he struck out 10 Giants while pitching for the Angels June 15, 2009. The difference last night was that all 10 came in the first six innings.

“That was probably the best I’ve felt as far as location-wise this season. I was pretty dialed in on hitting Vic’s glove,’’ Lackey said. “You’ve got to give him a lot of credit. His mix was incredible tonight. He called a great game.’’

Lackey has faced the Mariners twice this season, allowing two earned runs on eight hits over 16 innings. Of his 12 wins, nine have come at Fenway.

“That was the best I’ve seen the whole year. He had a great changeup, curveball, slider, and location. He was pretty much throwing the ball wherever he wanted,’’ Martinez said. “Every time I put my glove somewhere, he hit my glove. It was amazing.’’

Jonathan Papelbon pitched the ninth for his 31st save. Papelbon has blown three saves in games Lackey was lined up to win. But he took care of business this time as the Sox continued dreaming about the postseason.