Surgery might shelve Pena

Washington Nationals outfielder Wily Mo Pena will need surgery to repair a small tear in his left shoulder, a procedure that could put an abrupt end to his dismal season.

An enhanced MRI taken Monday on Pena’s shoulder revealed a small tear and impingement in his rotator cuff and fraying in his labrum, according to team orthopedist Ben Shaffer. Surgery will take place in the next seven to 10 days.

The Nationals won’t know for certain how long Pena’s recovery time will be until after the operation, but a club official said it’s possible the slugger won’t return this season.

The injury offers some explanation for Pena’s struggles at the plate this year. At the All-Star break, he is hitting only .205 with two homers and 10 RBI in 195 at-bats. Over the first six seasons of his big league career, Pena averaged one home run every 18.6 at-bats.

Manager Manny Acta said Sunday that Pena’s shoulder first started bothering him “far back” and that he was given a cortisone shot about a month ago to relieve the pain. The 26-year-old never asked out of the lineup or said he couldn’t play, and it wasn’t until the last week that the club decided to have the shoulder examined.

“Nobody’s 100 percent every single day,” Acta said. “Everybody has something that is bothering him…. I’m sure that if he wasn’t able to take this pain and play through it, he wouldn’t play through it.”

Pena has declined to speak about his shoulder and his struggles this season, which came after he signed a two-year extension that is paying him $2 million this year and includes a $5 million team option or $2 million player option for 2009.

“It hasn’t been easy, especially with all the expectations that were created around him after he played so well for us at the end of the season last year,” Acta said. “I’m sure that he probably is the last guy to think that he was going to be where he is right now.”