WASHINGTON -- Nationals right-hander Stephen Strasburg, on the disabled list because of shoulder stiffness, played catch in outfield Sunday without having any problems, according to pitching coach Steve McCatty. Strasburg threw as far as 60 feet.

"It went fine, very good," McCatty said. "In my mind he is fine. ... He felt free and easy. He felt good."

After he plays catch again Monday, Strasburg will have a bullpen session Tuesday and have a simulated game on Thursday in Arizona.

Manager Jim Riggleman doesn't believe Strasburg will need a rehab assignment before being taken off the disabled list. Riggleman declined to say when Strasburg's next Major League start will be.

"If he goes OK in the simulated game and then responds to that with a day or two of rest and then throws his bullpen session, he would not have to go to the rehab situation to start over. He would still be built up enough to continue on and pitch."

In nine Major League starts, Strasburg is 5-2 with a 2.32 ERA.

Zimmermann activated, sent to Triple-A

WASHINGTON -- The Nationals reinstated right-hander Jordan Zimmermann from the 60-day disabled list then optioned him to Triple-A Syracuse on Sunday.

Zimmermann, 25, was a combined 0-2 with a 2.38 ERA after six rehab starts with Class A Advanced Potomac, Class A Hagerstown and Double-A Harrisburg.

Zimmermann began the season on the DL because he was still recovering from Tommy John surgery. He had the surgery performed on Aug. 19, 2009.

The Nationals are hoping Zimmermann will be ready for big league action sometime this month.

Walker visits teammates after surgery

WASHINGTON -- Right-hander Tyler Walker was seen visiting teammates Sunday after having surgery on his right labrum and rotator cuff. He is out for the season and hopes to be ready for Spring Training.

Manager Jim Riggleman feels that Walker was hurting long before he was placed on the disabled list in June.

"He was probably pitching in pain for quite a while," Riggleman said. "I know that as he would pitch -- quite often if he threw a couple of innings and sit him down between innings -- it was a challenge for him. He felt that was the nature of being a reliever and it caught up with him. So I'm not totally surprised, but I guess to have both [injuries] is pretty devastating."