SEATTLE -- This was supposed to be a breakout season for Seattle Mariners first baseman Justin Smoak but about the only thing that broke was his nose.

Smoak, the featured player in the 2010 midseason trade with Texas for lefty Cliff Lee, had his otherwise injured-ridden season sweetened Monday night with his three-run home run that helped give the Mariners a 4-2 victory over the Oakland A's.

"It's been a lot of ups and downs, too much watching games and not playing," said Smoak, who has missed 41 games with a thumb injury, a fractured nose and a groin strain at various points in the season. "It's been a learning experience and I know what I need to do this offseason to get prepared for a full big-league season."

With the score tied at 1-1 in the sixth, Dustin Ackley drilled a two-out single to center. Mike Carp dropped a single into left center, sending Ackley to third. Smoak then connected on a 1-0 fastball for his 15th home run, into the right-field seats.

"This is a guy we believe in," Mariners manager Eric Wedge said. "I feel like he's going to have a real good year for us next year. I know he's going to work hard this winter to shore himself up to stay away from those injuries and be stronger.

"You saw what his capability is tonight. Those three-run homers are big separators for a ballclub. He's capable of doing that."

Smoak is hitting .318 with four home runs and 14 RBI since coming off the DL Sept. 2.

Jason Vargas (10-13) earned his career-high 10th victory. He worked eight innings, allowing one run on five hits, walking none and striking out career-high 10.

Miguel Olivo also hit a solo home run in the fifth, his 19th. That broke the Mariners club record for most home runs by a catcher, one more than both Kenji Johjima and Dan Wilson.

Brandon League finished the ninth, allowing a run on Josh Willingham's RBI groundout, scoring Coco Crisp from third. Crisp had opened the inning with a single and stole second and third to give him 48 steals. He's now tied for the league steals lead with New York's Brett Gardner.

League still managed to pick up his 37th save in 42 opportunities.

A's starter Brandon McCarthy (9-9) went the distance, allowing four runs on eight hits. He struck out six and walked no one. It was his fifth complete game this season.

It was the first time this season that McCarthy has given up more than one home run in a game.

"I thought my pitch selection was fine, I just didn't throw it where I wanted to and (Smoak) did what he's supposed to," McCarthy said. "It was supposed to be a cutter in and I kind of left it middle down, right where a lefty likes to drop his barrel into it and he didn't miss it."

The A's touched Vargas in the first. Jemile Weeks lead off the game with a double into the left-field corner. Crisp moved him to third with a right-side groundout. Hideki Matsui sent Weeks home with a flare single to left.

That broke Matsui's 13-game streak without an RBI, the longest stretch of his career.

No A's player reached second against Vargas after the first inning. At one point, he retired 14 straight batters.

Vargas finished the season strong with three wins in his last four starts and a 2.03 ERA. But before that he had a stretch from July 6 to Sept. 2 in which he went 1-8 in 11 starts.

"I always felt like he was strong; that was never an issue," Wedge said. "But you want to see him bow his neck and finish strong, for his own confidence for next year, and for his teammates and everybody to see that."

Vargas said he tinkered with some mechanical issues over the past few weeks that has allowed him to stay over the rubber more with better control of his fastball.

"It really seemed to help how the fastball was coming out of my hand," he said. "It seemed to make everything else a little better."

"I think the key for me next year is being able to maintain that consistency after the All-Star break. That seems the thing I've had to fight with the most. This year was another learning experience. I'll reflect on it a little bit and get ready for next year."

He added that reaching 200 innings (201) was a big step.

"I think 200 innings is what every starter shoots for," he said. "That means every starter is doing their job pretty good."

With one out in the fifth, Olivo tied it, hitting a 1-0 fastball over the left-field wall. Olivo leads the team in home runs and RBI (62). No catcher has ever led the team in either category.

Adam Rosales had a two-out single in the eighth, ending an 0-for-34 slide. His last hit was June 30, a span of 15 games.

Game notes
Wedge has had meetings with his players, his coaches and the front office all geared toward improving next season's results. "This is going to be arguably the most important winter that these guys are going to have," he said. "With all these young guys who are here and where they're at and what they've experienced this year, they need to understand what they need to do physically to make sure they're coming to spring training where they need to be and not leaving anything to chance. Believe you me, I'll know when I see these guys or talk to these guys in regard to what we've been talking to these guys about the last two or three weeks and where they come in next spring." ... SS Brendan Ryan (neck) and OF Casper Wells (head) will not play again. ... A's have a pair of injured players, OF David DeJesus (hip) and OF Cliff Pennington (oblique) who did not play Monday but manager Bob Melvin hopes to have both available Tuesday.