WASHINGTON -- Nationals left fielder Wily Mo Pena said he will have surgery on his left shoulder on Tuesday.
The procedure will be performed by Timothy Kremchek, the Reds' medical director, in Cincinnati.
Pena has a small tear and impingement in his left rotator cuff and he believes he will be out of action for at least two months, but the Nationals will know more after the surgery. Pena had been playing with the injury for over a month, but denied it to the media for weeks that he was injured.
It wasn't until late Thursday afternoon that he officially said that he had a problem with the shoulder. He also apologized to the media for being silent on the matter. Pena said there was a reason he didn't say anything in the past.
"[Baseball] is my life," said Pena. I live for baseball -- that's my career. I think everybody knew because of the way I was swinging and the way I was playing. The main thing is, I'm a tough guy and I want to play. So I just kept playing."
Pena is having the worst year of his career, hitting .205 with two home runs and 10 RBIs. He acknowledged that he had a tough time getting around on fastballs because of the shoulder.
"Last year, I was killing all those fastballs," he said. "This year, I would pop it up."
With Pena expected to go on the disabled list on Friday, the Nationals are expected to activate catcher Johnny Estrada from the DL. Estrada has played in only 17 games this year because of a sore right elbow.
The Nationals will have four catchers -- Estrada, Jesus Flores, Paul Lo Duca and Wil Nieves -- on the 25-man roster. Manager Manny Acta said that Estrada will come off the bench and get some playing time behind the plate.
"I have to see Johnny Estrada out there," Acta said. "We have to take a look at him. It's July. Other than that, we'll deal with what we have."
In Pena's absence, Lo Duca and Kory Casto most likely will see time in left field.
In other news, first baseman Dmitri Young participated in workouts late Thursday afternoon and Acta expects Young to be ready for the three-game series against the Braves starting on Friday.
Center fielder Lastings Milledge (right groin strain) is starting to hit off a tee, but there is no timetable as to when he will return.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.