(John McDonnell/The Washington Post)

Bryce Harper will begin a minor league rehab assignment Tuesday night at Class A Potomac, General Manager Mike Rizzo said.

Over the weekend, Harper said he hoped to head to the minors Wednesday or Thursday, while Manager Davey Johnson said he wanted Harper to begin Tuesday. Johnson relented Sunday afternoon and said he doubted Harper would be able to start playing until mid-week.

But after Harper worked out Monday afternoon at Nationals Park, the Nationals determined Harper could start playing in games without risking damage to his swollen left knee, which has sidelined him since May 26. Two weeks later, Harper received a cortisone shot from renowned orthopedist Dr. James Andrews to relieve bursitis in his knee.

On Saturday, Harper said he wanted to play six minor league games before he returns to the Nationals in order to regain timing with his swing. Johnson suggested Harper would need fewer games before he was ready to return.

Harper was impressive in his workout today, spraying line drives during batting practice and running well on the bases and in the field.

At Potomac, Harper will be reunited with Manager Brian Daubauch, his first professional manager at Class A Hagerstown. Harper, 20, looked forward to playing with several of his former teammates as well.

“I’m really excited to play for Potomac, actually,” Harper said Saturday. “Of course I want to play in the big leagues. I don’t want to be down there. But it would be a great experience to be with them again.”

If Harper’s rehab assignment lasts beyond the next few days, he could move Hagerstown and play alongside his brother, Bryan, a left-handed reliever.