(Alex Brandon / AP)

Ryan Zimmerman will play in a minor league rehab assignment starting Monday with plans on coming off the disabled list and rejoining the Nationals on Friday in Pittsburgh, Manager Davey Johnson said. Zimmerman has retroactively been on the disabled list April 18 with a hamstring strain, meaning Friday will be the first day Zimmerman is eligible.

This morning at Nationals Park, Zimmerman worked out with rehab trainer Steve Gober and bench coach Randy Knorr. He played catch, fielded groundballs and ran the bases. Some of Zimmerman’s throws hit Gober in the chest; some skipped by him or flew to the short fence behind him.

Before Zimmerman went on the disabled list, he made four throwing errors in a span of five games, setting off alarm about the state of his throwing arm following offseason surgery. Johnson said recovering from the hamstring pull has not inhibited Zimmerman from working on his arm strength.

“He’s still throwing,” Johnson said. “He’s throwing very good. I think we’re moving along. Zim was in a great frame of mind yesterday. He felt like it was really moving along and he’s going to be by it.”

Johnson said it had not been determined at which affiliate Zimmerman would play. Class A Potomac will play at home Monday, though, making it likely he’ll play there.

Once Zimmerman returns, the Nationals will likely send Anthony Rendon back to the minor leagues. When they called up Rendon, their top prospect, last weekend in New York, Nationals officials said they believed they would send him back to the minors for more seasoning upon Zimmerman’s return.