Adam Jones slowed down just before reaching third base following Chris Davis' hard double to left field in the fourth inning, then decided to keep going.
The speedy Baltimore center fielder should have went with his first instinct.
Jones was thrown out at the plate on a perfect relay throw from Oakland shortstop Stephen Drew, a costly mistake on a night the Orioles were knocked out of first place in the AL East.
"It changed the dynamics of the game," said Jones following Baltimore's 5-2 loss to the Athletics on Saturday night. "I just slowed down. Honestly, there's no reason why. There's no excuse why. It's one of those things you can't explain."
The Orioles have a lot of explaining to do after dropping their second straight on this nine-game road trip.
The loss dropped Baltimore a game behind first-place New York in the division and three behind Oakland in the AL wild card race with 17 games remaining.
"This time of year you've gotta make the plays," Jones said. "Every out is important, all 27 outs. We're playing good baseball, we just have do what has gotten us here."
Nate McLouth homered for Baltimore but the Orioles managed only one other run off Oakland starter Jarrod Parker and two relievers.
Drew hit his second home run with the A's and fourth overall, Chris Carter had a two-run double as part of a five-run third inning while Josh Reddick added two hits and an RBI for Oakland.
Parker (11-8) allowed two runs and seven hits over seven innings to win back-to-back starts for the first time since mid-July. The A's rookie right-hander struck out five, walked one and retired 11 of the final 13 batters he faced.
"He's maturing more and more as the season goes along," Oakland manager Bob Melvin said. "He's done it a couple times now where he's not off to the greatest start in the world but he's able to recover, think calmly and make some adjustments."
Sean Doolittle pitched a scoreless eighth and Grant Balfour worked the ninth for his 19th save.
Baltimore took an early 2-0 but starter Zach Britton (5-3) couldn't make it hold up.0
Coming off his worst outing of the season, Britton had four strikeouts but walked four and gave up five earned runs for the second consecutive start.
"This was a good series for us to take a couple games and I couldn't get the job done," Britton said. "We get two runs and then I put us into that hole right away."
He didn't get much support from Baltimore's offense.
The Orioles managed only two hits after the fourth inning and stranded a pair of baserunners in the ninth when Balfour got Endy Chavez to ground to third for the final out.
Parker got the Orioles to ground into a double play in the first but his error on a pickoff attempt in the second led to Baltimore's first run.
Jones singled and was leading off the bag when Parker's throw to Carter at first base went in the dirt and rolled almost to the Orioles bullpen. Jones raced to third then scored on Reynolds' double to left.
McLouth made it 2-0 with his third homer of the season that hit off the facing above the scoreboard in right field. It's only the ninth home run allowed this season by Parker.
Britton didn't allow a hit until the third when the A's scored five runs.
Drew's solo home run started the outburst. After Adam Rosales grounded out, Coco Crisp walked before Britton hit Jonny Gomes on his left elbow to put runners at first and second.
Reddick and Cespedes both followed with RBI singles, and Carter doubled both men home to make it 5-2.
"They are a good pitching club and we knew coming in here that runs were going to be at a premium," Baltimore manager Buck Showalter said. "You better get some runs across when you can take advantage of it."
Notes: Baltimore has hit into five double plays in the first two games of the series. ... The Orioles are 12-18 against teams from the AL West. ... Rookie RHP Dan Straily (2-0) pitches for Oakland in the series finale. ... LHP Randy Wolf (2-0) makes his first start since signing with Baltimore after being released by Milwaukee in late August.