SEATTLE -- Yoenis Cespedes just feels more comfortable when he plays the outfield.
Cespedes homered twice and Bartolo Colon won his seventh straight start to lead the Oakland Athletics past the Seattle Mariners 6-3 on Friday night.
Limited to DH duty for seven games because of a sore hamstring, Cespedes celebrated his return to left field with a pair of two-run homers.
"Evidently he likes to play the outfield," Oakland manager Bob Melvin said. "You could see his whole demeanor today, he was just in a better mood.”
Jed Lowrie and Coco Crisp also went deep for the Athletics, who maintained their one-game lead in the AL West over Texas.
Cespedes homered in the first inning and again in the ninth for his third career multihomer game -- all this month, and all when playing left field.
"I can't say I'm 100 percent yet, but it feels great to play in the outfield," Cespedes said through a translator. "When I'm in the outfield, my body's completely up, my body's on fire. The difference is when I'm a DH and I sit down in the dugout and I'm doing nothing, I feel like I'm going down a little bit.”
Cespedes' hitting took some of the spotlight off Colon's pitching, but the 40-year-old right-hander was on top of his game, too. Colon (10-2) gave up three runs and seven hits over eight innings, tying unbeaten Max Scherzer of the Detroit Tigers for most wins in the American League.
Colon is 11-1 in his career at Safeco Field, the best record for any pitcher with at least seven decisions in the Mariners' home park.
"He's a veteran guy. He knows himself. He knows what works," said Crisp, who hit a solo homer in the sixth. "It's not a fluke.”
Colon, who has relied heavily on his fastball this season, said he feels he's pitching as well as he has since winning the AL Cy Young Award with the Angels in 2005. He attributed his recent success to adding more off-speed pitches to the stream of fastballs.
"I think it's because I mix it up better than I did before," Colon said through a translator. "I was always a fastball guy, so now I'm mixing it more.”
Mariners manager Eric Wedge, however, said Colon can dominate with only his fastball.
"He knows how to pitch. He recognizes swings," Wedge said. "He does as good a job with his fastball, his movement, where it starts and where it finishes, as anybody in the league.”
Grant Balfour worked the ninth for his 18th save this season and 36th in a row dating to May 5, 2012.
Hisashi Iwakuma (7-3) lost at home for the first time this season, giving up four runs and six hits -- including three homers -- in seven innings. His home ERA rose from 0.92 to 1.46.
The matchup between two of the American League's top starters turned into a relative slugfest.
Iwakuma had never given up more than two home runs in a game, and it was the first time in 18 career home starts he allowed more than one homer. He has lost two starts in a row, both to Oakland.
"We really didn't get a whole lot of hits off of him," said Lowrie, who homered leading off the fourth. "We were able to get those big homers, that's the only way we scored off him.”
Nick Franklin hit a three-run shot in the third against Colon, the first time the pitcher had allowed a home run or more than two earned runs in a game since May 14, before he started his winning streak.
Cespedes gave Oakland a two-run lead in the first inning with a shot that bounced off the upper-deck railing above the left field out-of-town scoreboard. It wasn't the first big hit Cespedes has had against Iwakuma -- he is 6 for 15 with three homers against the Mariners' starter.
The Mariners were hurt by a baserunning blunder in the sixth. After a leadoff single, Kyle Seager was thrown out trying to take two bases on a passed ball. Kendrys Morales' single and Raul Ibanez's walk gave Seattle two on with one out, but the Mariners were unable to push a run across.
Oakland added two insurance runs in the ninth off reliever Tom Wilhelmsen. Lowrie led off with a single and Cespedes followed with another homer to left field, his 15th.
NOTES: Oakland C John Jaso was a late scratch because of a left palm abrasion he got when sliding Thursday. ... Seattle promoted pitching prospect Taijuan Walker to Triple-A Tacoma. Walker, the Mariners' top pick in the 2010 draft, was 4-7 with a 2.46 ERA and 96 strikeouts in 14 starts for Double-A Jackson. ... Two of Seattle's 2013 draft picks, Austin Wilson (second round) and Lachlan Fontaine (13th), took batting practice before the game.