Bryce Harper caught stealing in the first inning in Tuesday’s game. (Nick Wass/AP)

Bryce Harper is out of Wednesday’s lineup against the Pittsburgh Pirates after receiving treatment on his left knee the previous night, according to Manager Davey Johnson. Harper slid in Tuesday’s game, notably when caught stealing in the first inning, and was icing his knee after the game.

“I’m just resting him to be safe,” Johnson said. “Hopefully it’ll calm down.”

Harper missed 31 games, most of them in June, with left knee bursitis that required injections of cortisone and PRP (platelet rich plasma) to calm the swelling. A week into his return, Harper said he was pleased with how well his knee responded to playing. The 20-year-old has run, slid and dived without any noticeable problems. Harper said then there was minor swelling, but nothing that couldn’t be treated with ice.

Johnson said before Wednesday’s game that Harper went to get ice from the training room after Tuesday’s game. “He hasn’t been in there,” Johnson said. “He’s a pretty tough cookie.” It’s also worth noting that the Nationals are facing left-hander Francisco Liriano and Harper has hit .169 against lefties this season.

Johnson hopes will Harper’s knee will calm down enough for him to return to the lineup Thursday in the closing game of a four-game series against the Pirates. Harper has played every one of the Nationals’ 19 games since his return from the disabled list on July 1. He is hitting .214 (10 for 70) with only one home run, .329 on-base percentage and .329 slugging percentage in that span. His season OPS has been above .900 until last week.

Asked if he thought Harper’s knee was affecting his play, Johnson disagreed. “I don’t think so. You never know. He wants to play.”

Johnson had hoped to play his regulars every day in the second half as they hope to make a push for the postseason. But he conceded he may have to relent with Harper.

“I might need to check on him a little more,” Johnson said. “He hasn’t really been in the training room and that’s the good sign. Again, I’m not going to take any chances. It’s getting a little aggravated and we could go out and exacerbate it.”