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Bryce Harper’s occasional lack of hustle had been a simmering issue within the Nationals’ clubhouse, and it came to the surface Friday night after he jogged down the line with two outs in the eighth inning on a grounder that second baseman Daniel Murphy bobbled.

Manager Davey Johnson never had a chance to weigh in, and today he brought up a possible reason for Harper’s slow pace. Johnson believes there is a chance Harper is still favoring his banged-up left knee, which landed him on the disabled list for more than a month in June. Johnson said Harper may require minor surgery to remove an inflamed bursa sac.

“That was talked about a while back,” Johnson said. “That’s a definite option. It’s going to be up to Bryce and” medical director Dr. Wiemi Douoguih.

Harper still receives treatment on the left knee and wears a pad to protect it.

“I think it’s still an issue,” Johnson said. “I think it’s probably there. He can probably play with it. But if he headfirst slides or dives in the outfield, it’s probably going to flare up. Hopefully, he’ll get through the season.”

Still, Johnson did not excuse Harper’s jogging to first. Harper had sprinted after two grounders earlier in the game, and he has not complained to the coaching staff or publicly about his knee.

“My opinion is, you take nothing for granted,” Johnson said. “You hit a groundball, the guy could boot it. You run. Anytime you quit going hard, it’s a losing attitude. With him, I’m between knowing if he’s babying his knee, because he’s usually 100 percent. But I’ll talk to him.”

Johnson did not appear to have major concerns about Harper’s effort. But he allowed that he had noticed Harper coasting at times. He mentioned one example. Harper hit a flyball against the Braves at Nationals Park, and when he reached first he peeled away to the right side rather than making a turn. Johnson approached him in the dugout.

“I haven’t seen a lot of it. I’ve seen a little of it,” Johnson said. “The flyball, he made a right turn. I had to question him on that. I don’t know what’s going through his mind. I’ll have a conversation with him.”

Johnson had to address Harper’s situation today because he left last night’s loss in the fourth after he felt light-headed due to dehydration. “I pinch hit for myself,” Johnson said.

Once Johnson retreated to his office, medical personnel tried to administer an IV, but it didn’t take. “I’m too old,” Johnson said. “They couldn’t even find my veins. I gave them two tries. I said, ‘That’s it.’ I tried it another way. I said, ‘Just bring me some water.’ After a good night of sleep I feel great.”