CINCINNATI -- Washington got off to a great start against Cincinnati All-Star right-hander Edinson Volquez, but Volquez gained the upper hand as the Reds defeated the Nationals, 6-5, at Great American Ball Park on Sunday afternoon.

With the win, Cincinnati completed a sweep of the four-game series.

Volquez, considered one of baseball's best starters over the first half of the season, was behind, 3-0, after three innings because of control problems. In the third inning, Volquez walked three batters and hit Washington starting pitcher Collin Balester in his right hand. After some attention from the Nationals' training staff, Balester remained in the game.

"When I first got hit, I didn't know if it hit my hand, but then the pain started coming in," Balester said. "I'm feeling better. It's all right."

The Nats' scoring began in the third inning. Ronnie Belliard drove in the first run with an RBI single, and Balester came home when All-Star reserve Cristian Guzman hit into a force play. A bases-loaded walk by Dmitri Young forced home Felipe Lopez with the third and final run of the inning.

Beginning in the fourth frame, Cincinnati took back the momentum. The Nationals, who left nine runners on base, couldn't touch Volquez over the next three innings as the Reds made their comeback.

"We should have won the ballgame," manager Manny Acta said. "We caught Volquez on one of his bad days. We should have scored eight runs off him."

In the fourth inning, Cincinnati tied the score at 3-3 on Adam Dunn's three-run home run, and Balester could have already been out of the inning. After two quick outs, he had Ken Griffey Jr. behind in the count, 0-2, but Balester ended up walking the future Hall of Famer.

"I was getting guys ahead in the count and just kind of -- I don't want to say I lost my focus, but I was missing and then [walking] guys," Balester said. "I made that mistake to Dunn, and he made me pay for it."

In the fifth, the Reds took advantage of Wily Mo Pena in left field and Young at first base. With a runner on first, David Ross doubled near the left-field line. Pena had a tough time getting to the ball, and Joey Votto scored all the way from first base.

Volquez then came to the plate with the intent to sacrifice the runners. He bunted the ball hard to Young, who had a play at third to get Ross. However, the ball went under Young's glove for an error.

Two batters later, with runners on first and third, Jerry Hairston Jr. hit into a force play, scoring Ross.

Balester lasted 5 2/3 innings, giving up five runs on four hits.

"I like what I saw," Acta said of Balester. "He has a lot of learning to do, obviously. I think he made two mistakes, and it cost him the runs. ... Two outs, nobody on, and he doesn't smell the blood and ended up walking guys that cost him three runs."

Hairston's RBI single in the eighth inning gained the Reds an insurance run, and it came in handy, as the Nationals rallied for two runs in the ninth before the issue was settled.