WASHINGTON -- The Battle of the Beltways turned out to be a real battle.

It took Adam Jones' two-run double in the top of the 12th inning to help the Orioles defeat the Nationals, 4-2, at Nationals Park on Friday.

With the score tied at 2, Nationals right-hander Kip Wells was able to get two quick outs, but suddenly, he had serious problems getting that third and final out.

Reliever Danys Baez came to the plate and collected the first hit of his career, an infield single down the third-base line.

"I was trying to make contact and put the ball in play," Baez said. "When you put the ball in play, a lot of things could happen. It went to the right place. It stayed right there down the line. The third baseman was playing way back. The pitcher realized he didn't have a chance to get me out at first."

Things started to unravel for the Nationals after Baez's single. Brian Roberts followed and doubled near the left-field line to put runners on second and third. Jones was next, and he doubled near the third-base line to drive in Baez and Roberts.

"I could have gotten ahead of Roberts, thrown better breaking balls to Jones -- neither of those things happen," Wells said. "Stuff like that is going to happen, unfortunately. In my case, I have to continue to pound the glove and try to keep myself out of situations where stuff like that can happen."

The 12th inning spoiled a great effort by the bullpen. Ron Villone, Jason Bergmann and Joe Beimel pitched a combined three shutout innings.

The bullpen has been the Nationals' Achilles' heel all season, and after Beimel was able to get out of the inning in the 10th, manager Manny Acta was thinking that this is night the bullpen would hold the opposition.

That wasn't the case in the 12th inning.

"I got to be thinking, 'Boy, this is our night,'" said Acta. "I think that it's encouraging [the relievers pitched well] before Wells [came in]."

Right-hander Jordan Zimmermann started the game for Washington and had his best outing in almost a month. Before the game, Zimmermann had a simulated game in the bullpen and pretended that it was the first inning. The reason for the exercise was because he had given up 13 first-inning runs in his past five games.

The bullpen outing helped, as he didn't allow a run in the first inning and gave up two runs in seven innings. Zimmermann struck out seven batters and walked only one.

"He threw the ball very well," Acta said. "He was very aggressive. His fastball has serious life today. It showed because he basically manhandled all those lefties. He had a good tempo, good fastball, good slider for him."

Zimmermann said the outing was the best so far this season. All of his pitches were working.

"It's just fun to be out there and have the control that I had today," Zimmermann said.

After three innings, Zimmermann was behind, 2-0. In the second inning, Nolan Reimold hit a solo home run, while Jones singled to left field to drive in Roberts. Both runs came with two outs.

"I get the first two guys out and give up a couple of base hits -- yeah, it's frustrating," Zimmermann said. "But it was hot out there tonight. I battled as long as could. I'm pretty happy with the performance."

But the Nationals came back and tied the score in the bottom of the fourth inning, when Ryan Zimmerman took a 1-2 pitch from Rich Hill and hit a two-run homer over the right-center-field wall.

After that, the Nationals collected just one hit.

"Hill had a very good curveball today," Acta said. "He felt like he could go to it at anytime he was in trouble. He got our guys way off balance the whole day. Their bullpen threw the ball real good."

The Nationals are now 0-6 in extra-inning games this year. What can they do to reverse the trend? It's simple. Get a better bullpen and score runs.

"To fix it, you have to score runs in those types of situations and be able to hold the opposition. We just couldn't get anything going offensively. That cost us," Acta said.