Nationals outfielder Bryce Harper injured his left thumb in the third inning during a slide into third base. Pirates third baseman Jung Ho Kang tried to deke Harper, pretending he had the ball and leading to an awkward slide by Harper.
The Nats star appeared to be angered by the play, and Washington manager Dusty Baker was seen yelling into the Pirates dugout.
In the bottom of that inning, benches cleared when Nationals pitcher A.J. Cole threw a wild pitch behind the back of Kang.
Cole was immediately tossed by the home plate umpire Jordan Baker. Both benches and bullpens emptied, and players were involved in an ensuing scuffle near the mound.
Harper left the game and was replaced by Chris Heisey in right field for the bottom of the third. According to MLB.com, he is listed as day-to-day but will have X-rays taken on the thumb on Monday.
"You don't want that to happen," Harper said. "I understand the deke at second base, I understand the double play kind of thing, but that kind of thing is not part of the game."
The Associated Press contributed to this report.