In the bottom of the fourth inning and the bases loaded, Harper hit a three-run triple to right-center field off left-hander Robbie Erlin. As he was sliding head first, Harper jammed the thumb into the base. Harper stayed in the game and later scored on a single by Jose Lobaton.
"I think everybody swung the bat well tonight," Harper said. "I felt pretty good tonight. It was huge for [Ian Desmond] to come out. Lobaton is swinging great. [Adam LaRoche] is doing the same thing. Everybody is swinging it well."
Harper went 2-for-2 with four RBIs in the game. Nate McLouth replaced Harper in left field in the fifth inning. It's not known if Harper will miss any games.
"I went in the dugout and swung in the cage. I felt fine. I hit some homers … in the cage," Harper said. "It was a 6-0 ballgame. I went out in the outfield and it swelled up a little bit. I thought we were in a good spot. Matt did, too. I went out and got some treatment on it. Put some ice in there. … We'll see how I feel tomorrow and go from there."
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the time. He also could be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.