The bad news is that Harper has bursitis in the knee and will need to rest the knee to avoid further damage.
Harper is out of the lineup today against the Orioles and there's a good chance he'll sit again tomorrow as the Nationals attempt to get Harper's nagging knee issues behind them. Harper initially injured the knee when colliding with a wall at Dodger Stadium on May 13, then reaggravated the injury yesterday when sliding headfirst into second and third base in the first inning.
"The worst-case scenario is that it swells up and then it needs to be drained or even have that (bursa) sac surgically removed," Nationals medical director Dr. Wiemi Douoguih said. "That's something we want to avoid, and that's why we're shutting him down. From a structural standpoint, it's not harming any of the ligaments or tendons or cartilage in his knee, so that's what we're most concerned about. But we're trying to control it so it doesn't advance to the point that we don't need to take that sac out or take fluid out."
The Nats plan to "aggressively" treat the injury and then observe it over the next 48 hours, Dr. Douoguih said, and then will see how Harper responds. If the swelling in the knee has gone down by Wednesday, there's a chance Harper could return to the Nats lineup, serving as the designated hitter against the Orioles in Baltimore.
"DHing would probably be good; he wouldn't run into walls," manager Davey Johnson joked today. "There's a short porch in Baltimore, if I recall. So that would be a welcome thing."
DHing would prevent Harper from needing to navigate the outfield or make sliding catches, but he would still be at risk when running the bases and hitting.
Dr. Douoguih said he would leave the decision of whether Harper should DH to Johnson and the Nats' baseball decision-makers, but "if the inflammation's under control, we can recommend he get out there and compete," Dr. Douoguih said.
Harper said yesterday that he thought this would be an injury that he'd need to deal with all season. Dr. Douoguih and Nats head trainer Lee Kuntz said today that's not necessarily the case.
"Once this thing is better, it should be better," Dr. Douoguih said. "It shouldn't bother him. Sometimes it can nag and last for a couple weeks and other times it goes away in 48 hours. We'll just have to treat it and see."
"That's why we want to get this inflammation down," Kuntz added, "so we can put that worry out of his mind and out of our mind."
Harper is batting .287 with 12 home runs on the season, but has hit just .179 over his last 21 games. Since returning from the wall collision in Los Angeles, Harper has just three extra-base hits in 31 at-bats.