Atlanta, GA -- (Sports Network) - The Washington Nationals placed outfielder Wily Mo Pena on the 15-day disabled list and activated catcher Johnny Estrada from the 15-day DL on Friday.

Pena has a small tear in his left rotator cuff and will have surgery on the shoulder early next week. He is expected to be sidelined at least two months.

In 64 games this season Pena has struggled with the bat, hitting just .205 with two homers and 10 RBI. A reason for his limited production was most likely the injured shoulder, as he claimed to have been playing through the injury for at least a month.

Estrada has been on the DL since early May with an elbow injury. The 32-year old started behind the plate in Friday's 7-6 loss to Atlanta and went 0- for-4.