(Jonathan Newton/The Washington Post) (Jonathan Newton/The Washington Post)

Barring any setbacks, Bryce Harper is expected to begin his rehab assignment Tuesday at Class A Potomac, Nationals Manager Davey Johnson said. Harper, who has not played since May 26 with left knee bursitis, ran in the outfield and took indoor batting practice  Thursday and  Friday, Johnson said.

Harper felt “fine,” according to Johnson, the day after a round of baseball activities Thursday. Harper is expected to remain with the team until Monday, Johnson said. Harper received received a cortisone and PRP (platelet-rich plasma) shot from orthopedist James Andrews on May 10 and a week later was cleared by  the Nationals’ training staff  to begin walking again without a knee brace. Harper declined to talk with reporters before Friday’s game.

The Nationals do not have a firm timetable for his return, which is dependent on how his knee responds to activity and playing again in game action next week. It’s also unclear how many rehab game he would need. Potomac is home from Friday until Thursday, and the Nationals are home until then and begin a series in New York on Friday, a potential target for Harper’s return.

“Knowing Harp, he probably won’t need much,” Johnson said. “It’s not so much timing as it is just seeing how he feels and how the knee holds up to being out there for nine innings.”

When Harper works out and plays again, he will be wearing a knee pad on his left knee. It’s likely Harper could aggravate the injury if he slides on it and hits it again. Harper has said it doesn’t matter which way he slides,  head first or feet first, he still hits his left knee. Even when he tucked his left knee under his other leg sliding for a catch in the outfield, he still hit his knee.

“He doesn’t know how to slide but one way,” Johnson said. “He’ll put every precautionary measure on his knee. And just gonna have to play. We’re not going to give him sliding drills. He’s just gonna play.”

>>> Roger Bernadina, who played half an inning on Thursday after not starting the previous two games because of an eye infection, said he is feeling better after visiting the eye doctor on Thursday.

Chad Tracy, who was dealing with a stiff back the past two days, is also feeling better and available after receiving treatment, Johnson said.

Tyler Clippard will be unavailable on Friday against the Rockies, Johnson said, because he  threw 1 2/3 innings on Wednesday on Philadelphia and warmed up on Thursday but didn’t enter the game in the eighth inning as Jordan Zimmermann worked out of a jam.