Reds starter Kyle Lohse gave up six runs, five earned, on eight hits over 4 2/3 innings. He walked four and struck out four. But he was having decent night until being derailed by a five-run Oakland fifth inning, capped by Mark Ellis' three-run homer.
"Even when I was going through quick innings, it wasn't like I had my best stuff out there," Lohse said. "I was falling behind guys but making good pitches when I had to."
The Reds (27-44) have lost five of their last six games to fall 17 games below .500 and 12 1/2 games out of first place -- both season highs.
Jason Kendall started the big inning with a leadoff single. Lohse had the next batter, Travis Buck, down 0-2 but lost him to a walk. In perhaps the most pivotal play of the night, Mark Kotsay smoked a sharp grounder to Brandon Phillips. The ball took a short hop at the second baseman's feet.
The ball went through for a single to right field that loaded the bases with no outs. If Phillips made the play, it could've been a double play and then Lohse has a man on third with two outs.
"It kind of opened up the floodgates," said Lohse, who entered the night 2-2 wit a 2.37 ERA over his previous four starts.
Lohse picked up an RBI groundout from Nick Swisher before cleanup hitter Eric Chavez hit a sacrifice fly. Jack Cust walked on a 3-1 count to keep the inning going.
"They're real selective over there even when they're ahead in the count," Lohse said. "He just didn't chase. I walked him on a slider. I went back and looked at it, but I don't know how you take it as a ball."
That free pass set up Ellis, who launched a three-run homer over the left-field fence. There may have been four innings left, but that was the ballgame.
"It was a tough inning," Lohse said. "You're trying to get out of it with minimal damage. I thought I got that. Then I made the mistake to Ellis. That pretty much put it out of reach the way [Joe] Blanton was throwing."
Blanton (7-4) cruised through an eight-inning outing and dispatched the Reds in a quick two-hour, 10-minute game. After the fifth, Cincinnati was quiet, spraying four hits but getting only one runner into scoring position.
The Reds' only run crossed in the third when Alex Gonzalez scored on Norris Hopper's hard-hit 6-4-3 double-play groundout.
Blanton allowed seven hits without a walk and struck out five.
A Gonzalez fielding error extended Oakland's first inning. With the bases loaded and two outs, Lohse was poised to escape until Gonzalez muffed a routine grounder that allowed Buck to score.
It was Gonzalez's 12th error of the season. Cincinnati is 9-26 in games where it commits an error this season.
"To get out of the first inning after the error with just one run was big," Reds manager Jerry Narron said. "I thought we were going to get out of the fifth just giving up two after they loaded the bases with no outs. We would have taken that."