UPDATED, 8:50 p.m.: Bryce Harper, in his first action in over a month, played three innings in the first game of his rehab assignment at Class A Potomac on a steamy Tuesday night in Woodbridge. Harper, hitting second, went 1 for 1 with a double, walk and run scored. He started in left field and saw little action defensively, other than running back to watch a drive go over his head, hit the warning track and bounce over the fence for a ground-rule double.

Harper, who wasn’t made available to reporters based on a directive by the Nationals public relations staff, appeared to be uninhibited by his left knee. Wearing a knee pad under his jersey pants, Harper ran with what seemed to be his usual speed around the bases.

In his first at-bat against Myrtle Beach Pelicans starter Alec Asher, he blooped the second pitch into shallow left field, a ball the shortstop raced back to catch but narrowly missed. Harper, running hard, rounded first base easily and got to second for a stand-up double. “He was flying,” said Potomac Manager Brian Daubach, who managed Harper in his first professional season in Class A Hagerstown in 2011. “That’s as good as I’ve seen him run.”

Harper was then picked off at second by Asher, taking too large a lead off the base and diving back on his stomach towards the base. The head-first slide appeared to have little effect on his knee. “He had a real aggressive lead and he was looking to steal third, and for me that’s a good sign,” Daubach said.

In his second at-bat, Harper drew a seven-pitch walk. On a two-out single to right by Jason Martinson, Harper looked like his old self: he ran hard from first to second and his helmet flew off just before he got to third base. He scored easily on a subsequent single by Adrian Nieto, quickly grabbing Nieto’s stray bat around home plate and, from one knee, waving in Martinson.

A scout in attendance agreed that Harper ran with his normal vigor and speed, and was actually pleasantly surprised that the outfielder did so and didn’t start slow.

Fans filled old, creaky Pfitzner Stadium to see Harper, cheering and applauding loudly before both of Harper’s plate appearances. He acknowledged the crowd as he walked to the plate in his first at-bat by touched the brim of his helmet. A large crowd gathered around the batting cage underneath the right field bleachers 30 minutes before the game to watch Harper hitting soft toss batting practice. More police officers than normal were at the stadium, including one who trailed Harper before the game.

Harper, should his knee respond well to playing, is expected to log about six innings Wednesday and then play a full game on Thursday. He is expected to rest on Friday and then play another full game on Saturday, likely when Class AA Harrisburg is at Bowie, a chance for him to face better pitching ahead of returning to the majors. He is then scheduled to rest on Sunday before rejoining the Nationals at home against Milwaukee.

Harper took full batting practice in the afternoon and took infield/outfield with the team, many who were with him in his first season at Hagerstown. “He looks the same old Harp,” Daubach said. “I know he was excited to get out there.”

ORIGINAL POST, 6:30 p.m.: Bryce Harper is slated to play three to four innings in the first game of his rehab assignment at Class A Potomac on Tuesday but isn’t expected to rejoin the Nationals until the beginning of next week. He will be wearing a pad on his left knee.

Harper, who hasn’t played since Mary 26 because of left knee bursitis, could return to the Nationals when they open a four-game series against the Milwaukee Brewers on Monday, according to Manager Davey Johnson. It was originally expected that Harper could rejoin the Nationals as soon as this weekend in New York. Harper had wanted to play six minor league rehab games but Johnson wanted fewer.

“I doubt he’ll be able to make [for this weekend] that quick,” Johnson said. “He’ll probably do three or four innings [Tuesday], and then if there’s no problem, gradually up it. He only has one [speed] – 150 percent. Even if it’s just three innings, he ain’t going to be babying it. He don’t know how to do that. But I’m hopeful the knee doesn’t react to him playing.”

Harper is hitting second and starting in left field for Potomac, and wearing No. 32 because Potomac starting pitcher Blake Schwartz already wears Harper’s normal No. 34. As he moved through the Nationals minor league system after he was drafted in 2010, Harper skipped Potomac, in part, because of the poor field conditions. The draining system was fixed prior to the 2012 season. Harper will be reunited with Manager Brian Daubach, his first professional manager at Class A Hagerstown.

Harper ran and warmed up before Tuesday’s game without any noticeable limp and with ease. He took flips in the batting cage about 30 minutes before the game, a large crowd watching nearby.

The tentative plan, if Harper and his knee respond well, is for him to play three to four innings on Tuesday and then jump to as many as seven innings on Wednesday. He would then play a full game on Thursday at Potomac and rest on Friday. He would then be expected to play another full game on Saturday, likely when Class AA Harrisburg is at Bowie, a chance for Harper to face better pitching ahead of returning to the majors. He is then scheduled to rest on Sunday.

Harper has already worked out twice at Nationals Park ahead of beginning his rehab assignment. He will not speak with reporters after Tuesday’s game, according to a directive by the Nationals’ public relations staff.

I’m not so much worried about his timing as I’m just how he reacts after he plays on [the knee],” Johnson said.

More to come after the game.