Bryce Harper with Potomac on Tuesday. (Nick Wass/AP)

Bryce Harper was scheduled to play the first full game of his rehab assignment on Thursday with Class AA Harrisburg at Bowie, but a long and arduously slow game cut short his outing. He played only six innings in left field and went 2 for 4 with a walk, single, two-run triple, two runs scored and a strikeout in his last plate appearance in the top of the seventh inning before he exited. He saw relatively little activity defensively in left but ran hard and well on the bases, even sliding twice.

This was the third game of the rehab assignment for Harper, who hasn’t played for the Nationals since aggravating his left knee bursitis on May 26. Thursday was his first game with Harrisburg, a chance for him to face tougher pitching ahead of his expected return on Monday.

“He looked good, swung the bat well and made a couple plays in the outfield,” Harrisburg Manager Matthew LeCroy said. “I thought he moved around good on the bases. It was a good sign.”

Because of a high-scoring game and three Bowie Baysox pitching changes over the first seven innings, Harrisburg and Harper received a heavy load of at-bats early in the game. Harper logged three at-bats in the first three innings. Nationals officials decided to end Harper’s night after he struck out in the top of the seventh, believing the outfielder had essentially completed a game. Even though Harper was slated to play nine innings, the Nationals didn’t allow him to speak with reporters, sticking to a policy issued in a memo earlier this week that the outfielder wouldn’t be available until he played a full game.

“It was just too long,” LeCroy said of Harper’s night. “Two and half hours, two-forty, sorta similar to playing a full game.”

Harper is tentatively scheduled to take Friday off and play nine innings on Saturday with Harrisburg. Nationals Manager Davey Johnson was curious to hear how Harper fared with Harrisburg after Washington’s game ended, perhaps even leaving the door open that the outfielder could return this weekend if he is ready — but that may not be likely. “I’d like to have him in there,” Johnson said. “He can’t be hurting too bad.”

Harper, on the disabled list, hasn’t played in the majors since May 26 and received a cortisone and PRP injection in his left knee from James Andrews on June 10. In three rehab games so far, he is 4 for 8 with three extra-base hits, two walks and three RBI.

Harper tested his knee the most when running hard on a triple in the second inning. He fell behind 0-2 quickly but then drilled a line-drive two-run triple to center field. He tore around the bases, losing his helmet after passing second base. He slid into third base on his left knee and popped back up instantly. After his first-inning walk, Harper jumped and slid back into the base on his stomach and legs on a pickoff move.

LeCroy said Harper told him that his knee felt “fine” and that he felt “strong.”

Harper also ran hard around the bases in the first inning. He drew a seven-pitch walk and, on a double by Justin Bloxom, scored from first base. Harper ran well, perhaps not as hard as on the triple, particularly when he neared third base and reached up to hold down the helmet that was, as it normally does with him, started to fly off.

“Scoring from first and then the triple, for me, I saw some aggressive base running and running like I’m normally used to watching him run,” LeCroy said.

In the field, Harper got little action. He fielded a soft-rolling single through the infield and threw it back in. He caught a sky-high popup that required little running. The most he moved in left field on Thursday was a flyout to end the sixth inning in which he ran about 30 feet to his right.

The Nationals were more worried about how his knee would hold up to the running around the bases and the outfield than his timing. But Harper’s timing and ability to work pitchers was still intact, even though this week was the first time he has played in a month. He saw 24 pitches in five plate appearances.