WASHINGTON — Nationals outfielder Wily Mo Pena went on the 15-day disabled list today because of an injured left shoulder that will require surgery. He was hitting .205 with two homers and 10 RBIs.

Washington also reinstated catcher Johnny Estrada from the 15-day DL. He had been sidelined by a right elbow injury, then hit .281 with a homer and 10 RBIs during a 16-game rehab assignment with four minor league clubs. Estrada is hitting .179 with three RBIs in 17 games with the Nationals this season.

The Nationals, who entered Friday with a majors-worst record of 36-60, have made 21 DL moves this season, involving 15 players.

Pena is making his second trip to the DL in 2008, after missing 12 games at the start of the season with a strained side muscle.

Only one member of Washington's opening day lineup — All-Star shortstop Cristian Guzman — has not spent time on the disabled list this season.