WASHINGTON (AP) As Nationals star Bryce Harper took an awkward tumble in the wet outfield Thursday night, he felt something few associate with the brawny slugger:
Harper might have escaped a serious injury, straining his left hamstring while making a throw in Washington's 5-3 loss to the Tampa Bay Rays.
But with immense talent and injury ridden past, even Harper had trouble keeping calm.
''I've had problems with my left knee before - I've had surgery on it,'' Harper said. ''So you know, it was definitely really scary.''
Manager Matt Williams said Harper had a mild strain and would be evaluated Friday. He gave no estimate on how long Harper might be out or whether he would need to go on the disabled list, though Harper indicated he may be day-to-day.
''Be smart about it, of course,'' Harper said. ''I want to be in there, but if I don't feel right tomorrow, then maybe taking that day off might help me a little bit.''
Harper is hitting .344 with 22 home runs and 52 RBIs. A two-time All-Star at 22, he has dealt several lower body injuries through his career, and had surgery on his left knee after the 2013 season for a bursa sac. Harper also missed roughly a third of last season with a thumb ligament injury.
A prolonged absence would add to the injury difficulties for the Nationals, who lost three of four to the AL East-leading Rays to fall to one game above .500.
Doug Fister (2-3) came back from a month out with forearm tightness Thursday, but allowed five runs in 5 1-3 innings. Starter Stephen Strasburg (neck tightness) could potentially return to the team after his next bullpen session.
Outfielder Jayson Werth is aiming for an Aug. 1 return from a left wrist contusion, and infielder Ryan Zimmerman went on the disabled list last week with plantar fasciitis in his left foot.
''It's time to step up. Everybody,'' Williams said. ''We look forward to doing that tomorrow.''
Harper fell on the damp grass while trying to throw home on Asdrubal Cabrera's single in the sixth inning. As he planted to throw, his right leg slipped and his left leg buckled.
Harper held his left leg while down on the ground for a few minutes and then gingerly walked off the field under his own power, escorted by members of the Nationals' training staff.
Harper's throw went wildly into the dugout during a four-run inning for Tampa Bay. There had been a 17-minute rain delay in the fourth.
''That wet surface played a big part in that, and it's a bummer it happened,'' Harper said.
Said Williams: ''Conditions are conditions.''
Joey Butler homered and pinch-hitter David DeJesus had a two-run triple for the AL East-leading Rays.
Chris Archer (8-4) won his fifth straight decision despite allowing three runs on a season-high eight hits in five innings. Brad Boxberger pitched the ninth for his 16th save.
''I think taking three of four from anybody is big,'' said Rays manager Kevin Cash. ''We were fortunate to come out of here with three wins.''
Yunel Escobar got five hits for the Nationals for the third time this season.
Rays outfielder Steven Souza Jr. joined Nationals starter Jordan Zimmermann on the field pregame to accept the 2014 award for the the defensive play of the year from MLB.com. Last year with the Nationals, Souza's diving catch completed Zimmermann's no-hitter against the Miami Marlins on the final day of the regular season.
Rays: Pregame rain prevented OF John Jaso (left wrist contusion) from taking on-field batting practice for the first time this season. ''We wanted him out there and it didn't work out,'' Cash said. ''He'll probably go ahead and take 500 swings now in the cage.''
Nationals: Strasburg (neck tightness) was throwing on the field the day after a rehab start, and will throw a bullpen in the next couple days. . RHP Aaron Barrett (bicep strain) hasn't returned to throwing after going on the DL last Friday, Williams said.
Rays: A five-game road trip continues when RHP Nathan Karns (3-3, 3.67) faces Cleveland RHP Carlos Carrasco (8-5, 4.38)
Nationals: 22-year-old rookie RHP Joe Ross (1-1, 3.46) gets his third career start against Pittsburgh Pirates RHP A.J. Burnett, who will be making career start No. 418.