WASHINGTON -- Following Saturday's 10-2 loss to the Braves, the Nationals optioned right-hander Jason Bergmann to Triple-A Columbus and activated closer Chad Cordero from the 15-day disabled list.

The Nationals are also expecting to activate outfielder Wily Mo Pena from the DL on Sunday. There is no word on who will be taken off the 25-man roster when Pena returns.

Cordero missed the first 12 games because of right shoulder tendinitis, but he recently pitched two rehab games and didn't give up a run in two innings for Class A Potomac.

As far as Bergmann is concerned, it was a complete collapse. After posting the best ERA in Spring Training, Bergmann had a tough time getting people out once the season began, giving up 16 runs over 12 1/3 innings.

Bergmann's worst game came on Wednesday against the Marlins. He was cruising the first four innings, but in the fifth inning, the Marlins scored seven runs.

On Saturday, it was more of the same as Bergmann gave up four runs against the Braves.

"When you don't throw well and the team is losing, somebody has to take the hit," Bergmann said. "I was not throwing well, and that contributed to most of our losses. I hope these guys can turn it around."

General manager Jim Bowden couldn't promise Bergmann that he would back in the big leagues because there are other talented pitchers, such as Collin Balester and Tyler Clippard, in the system. In his last two innings, Bergmann gave up 11 runs.

"Whoever pitches best here is going to pitch here," Bowden said. "It's a little different than before. That being said, [Bergmann] needs to step it up. He has three pitches. He has enough stuff. He just needs to execute it."

The Nationals need hitting so badly that they've decided to limit Pena to just one rehab game for Columbus before activating him from the disabled list on Sunday. Pena didn't play the first 12 games of the season because of a strained left oblique.

Pena is expected to be the power threat that could help people like Austin Kearns see better pitches to hit.

"We could have taken our time on Pena, but he has gotten better quicker than we expected," manager Manny Acta said. "This is not about attitude and confidence. This is about a couple of two-run doubles. That's what we need.

"Right now, we are just not doing it. Nothing gives you happiness or confidence -- whatever you want to call it -- more than a couple of two-run doubles. Right now, we need a guy like him that can intimidate, get up to the plate [and] maybe take a swing and make everybody jump."