BALTIMORE — Two annoying and persistent shortcomings proved too much for the Baltimore Orioles to overcome against the surging Oakland Athletics.

Tommy Hunter gave up more two home runs and the Orioles again failed to come up with a timely hit in a 6-1 loss Saturday night, their fifth defeat in six games.

Hunter (4-6) allowed five runs and seven hits in 5 2-3 innings. The most damaging blows were long balls by Yeonis Cespedes and Chris Carter, each of whom connected with a man on.

Hunter has yielded 24 homers this season, at least one in every one of his 16 starts but two. The latest two were irksome because they ruined an otherwise decent outing.

"Trust me, I'm not changing anything about what I did tonight," he said. "I really wouldn't. They got me and they got me on two pretty good pitches. I'd probably throw them again. But now knowing their approaches, that's probably the only thing I'd change about it."

Giving up home runs has been Hunter's biggest flaw this season, and Baltimore's failure to produce with runners in scoring position has been the offense's most glaring weakness.

Baltimore went down in order only once, but stranded 11, went 0 for 6 with men in scoring position and lost for the fifth time in six games. Were it not for Nick Markakis' ninth-inning homer off Evan Scribner, the Orioles would have been blanked for the eighth time.

"I'm not saying anybody's trying to do too much," cleanup hitter Adam Jones said. "I think we can just lay back a little bit and relax at the plate and just get back to playing the way we have been. It's a tough stretch right now because it's the second half and every game is important."

Jemile Weeks had three hits and scored twice for the A's, who improved to 18-3 in July.

Bartolo Colon (7-8) scattered seven hits over 5 2-3 shutout innings, striking out five and walking one, to earn his first win in six starts since June 12. The 39-year-old is 12-8 with a 3.10 ERA lifetime against Baltimore, dating to 1998 when he pitched for Cleveland.

Oakland broke on top in the fourth when Weeks led off with a single and Cespedes hit his 14th home run. The Orioles got a hit in each of the first four innings but failed four times to produce with runners in scoring position.

The Athletics made it 3-0 in the fifth. Kurt Suzuki hit an opposite-field double to right and scored on a single by Eric Sogard.

Carter chased Hunter in the sixth with a drive to left after Seth Smith hit a leadoff single. It was Carter's eighth homer since rejoining the A's on June 29.

"We're seeing Chris Carter (be) the guy we all hoped and anticipated him being," A's manager Bob Melvin said. "Right now, he's quite a force and one of the reasons that, offensively, we've been so good this month."

In the bottom half, the Orioles got singles from Wilson Betemit and Mark Reynolds before Jordan Norberto struck out Omar Quintanilla to end the inning.

Jones grounded out in the Baltimore seventh with two outs and runners on second and third.

Weeks singled and scored on a triple by Cespedes in the eighth.

NOTES: After the game, the Orioles optioned RHP Miguel Socolovich to Triple-A Norfolk. ... A's leadoff hitter Coco Crisp left in the eighth with tightness in his left hamstring. ... Baltimore DH Jim Thome did not play because of back spasms. ... Orioles 2B Brian Roberts (groin strain) began a minor league injury rehabilitation assignment with Class A Aberdeen on Saturday. Manager Buck Showalter said Roberts would be reevaluated after two games there. ... Baltimore C Matt Wieters reported that his tight right biceps felt much better and said he expected to play Sunday. He has missed two games with the injury. ... Oakland OF Josh Reddick was absent from the starting lineup a day after he crashed into the right-field scoreboard to make a game-ending catch. ... Travis Blackley (3-2) makes his first career start against Baltimore in the series finale. Wei-Yin Chen will pitch for the Orioles. ... Oakland LHP Dallas Braden's recovery from shoulder surgery was stalled in Arizona when he strained his left groin while throwing. He has been shut down.