Updated at 5:01 p.m.
Bryce Harper was due to have an MRI performed on his swollen left thumb late Saturday afternoon after the Nationals outfielder was examined by a hand specialist during the club's 4-0 victory over the Padres.
The MRI is standard procedure, and the Nationals remain hopeful that the injury is not serious, but Harper's continued swelling and discomfort were enough to convince the club to take this next step.
"He showed up this morning a little swollen," manager Matt Williams said following the game. "The hand specialist saw him during the game. He's currently having an MRI. The X-rays [taken Friday night] are negative. He's having an MRI this afternoon and we'll have more details tonight, in the morning. But he's a little swollen today."
Harper jammed his thumb sliding into third base Friday on a third-inning triple. He briefly remained in the game and played left field in the top of the fourth before departing with the thumb swelling up.
Harper was held out of the Nationals' lineup Saturday, and though Williams said he would have been available off the bench in an emergency, he's unlikely to play in Sunday's series finale against San Diego. With an off-day on Monday, the earliest Harper would return to the lineup is Tuesday in Houston.
"I would imagine so," Williams said. "Make sure that it's good."
Harper was not in the Nationals clubhouse while reporters were present before or after Saturday's game, but the 21-year-old outfielder was in good spirits after Friday night's game and said he didn't believe the injury was serious.
"I didn't think so," he said. "When you hit it, you know whether it's pretty serious or not. It just swelled up a little bit and that was pretty much it."
The Nationals didn't feel the injury was serious enough Friday night to arrange for a quick MRI, electing instead to have the hand specialist (who was already coming to the ballpark to look at injured regulars Ryan Zimmerman and Wilson Ramos) examine Harper on Saturday.
"It could've been done last night, but you have to make special arrangements," Williams said. "He probably wasn't going to play today anyway. Then we had the hand specialist here to see all three guys today: Zim, Wilson and now Bryce. He was coming in anyway, so we figured have him look at Bryce, too. So now he's going to get an MRI, get a picture on it and see."