BOSTON — The real Dustin Ackley has slowly shown up for the Mariners the past week or so but could not arrive in time to save this blowout.

Ackley wound up with a single Monday night to extend his hitting streak to 10 games during a 6-1 loss to the Boston Red Sox. But the Mariners had little chance once one of their starting pitchers again got lit up early and was joined by his hitters in taking the team out of the game.

The Mariners were toyed with early by Red Sox starter Jon Lester, a Bellarmine Prep of Tacoma product, and were pretty much cooked once they found themselves in an early five-run hole.

"His cutter was really good," Ackley said of Lester. "That thing looked like his fastball and it just breaks off at the last minute. When you have a pitch like that, you're going to miss barrels a lot."

And miss them Lester did, giving up just an infield single the first five innings and not allowing a ball out of the infield until the fifth. He needed just 55 pitches to get through the first five innings and 119 for his second complete game this season and eighth of his career.

The Mariners got to Lester for some late hits and a run on a Kyle Seager ground out in the ninth. But a pair of fourth-inning home runs by Daniel Nava and Kelly Shoppach off starter Jason Vargas had already settled this one in front of 37,334 fans at Fenway Park.

"I should have done a better job of keeping us in the game, that's the bottom line," Vargas said.

The left-handed starter, who had looked impressive in an eight-inning outing to beat Detroit at Safeco Field last week, admitted he had little more than a fastball working for him.

"It was kind of opposite from my last outing where I really couldn't throw a changeup for a ball, when all of them tonight were balls," Vargas said. "It was just one of those nights where I had to go out there and battle. I was really more upset with the fourth inning more than anything. I had a chance to keep us in the ballgame, even with mediocre stuff.

"But I let the bottom part of their lineup get ahead of me and it kind of put us out of the ballgame right there."

Vargas fell behind 2-0 in the first inning on a Dustin Pedroia walk and back-to-back doubles by David Ortiz and Adrian Gonzalez. The Ortiz ball off the Green Monster in left was one of those Fenway flies that might have been caught in other parks.

But the Gonzalez ball was lined into the left-field corner pretty hard. Some infield singles off Vargas in the second inning were also hard-hit balls, while the fateful fourth inning saw long balls rocketed over the left-field wall.

Nava was playing in only his sixth game since being called up from the minors this season with an injury-ravaged Boston club, but got all of Vargas' fastball with a runner on and sent it just over the 37-foot high Monster into the first row of seats. Shoppach came up two batters later and destroyed a Vargas changeup left over the middle of the plate.

Vargas shut down the Red Sox his final two innings before leaving after six trailing 5-0. But the damage was done.

"I've got to do a better job of keeping us right where we are even though I didn't feel my best," Vargas said.

Seattle didn't really start getting to Lester until the sixth, when Ackley's single put two on with one out. But Casper Wells popped out and Ichiro grounded into a fielder's choice to end the threat.

The Mariners had three more hits off Lester in the seventh, but caught a bad break as Seager lined into a double play with two on and none out.

"In my at-bat, he threw a couple of balls, got behind 2-0 and had to throw the fastball," Ackley said. "And I think, when you're in that position, balls are going to get hit fairly well. I think that was really the only time where he was getting hit when he was getting behind and having to throw his fastball and not the cutter, the curveball and stuff like that."

The Mariners have scored two runs or fewer in three of their past four games and 14 overall. They are 1-13 in such instances.

"These guys are, to a man, working on certain things," Mariners manager Eric Wedge said. "I was pleased with some of the at-bats and approaches we had and some of them are still struggling to get what they need to do from a mental point to hit pitches."

Wedge said he has seen positives out of Ackley, Justin Smoak, Michael Saunders, Seager and others when it comes to fundamentals. But the team still has work to do on its mindset and approach to hitting.

"In order to barrel up on the ball more consistently," he said, "we still have a ways to go."

Geoff Baker: 206-464-8286 or gbaker@seattletimes.com. On Twitter @gbakermariners.