It marked Harper's second career ejection. The first one came on Aug. 29, 2012, against the Marlins after he slammed his helmet down while trying to beat out a ground ball.
Roger Bernadina replaced Harper in left field and went 2-for-4 with a run scored.
"I was going to give Harper the day off, but I didn't expect it to go that way," Washington manager Davey Johnson said.
Harper, who is nursing a sore left side, wouldn't say what happened during the incident. In fact, he said he didn't know what caused it.
"It's just something that happened. I'm glad it didn't cause the outcome of the game where we are losing. We got the 'W' today and things like that happen," Harper said.
Hirschbeck explained to MLB.com why he ejected Harper from the game.
"First of all, he put both arms up in the air. To me, I felt like that's showing me up," Hirschbeck said. "I yelled at him and warned him to stop. And then he continued and he slammed his bat down. I actually warned him again and then the next thing he slammed his helmet down, and I felt three warnings are more than enough."
Johnson said that Hirschbeck is a good umpire and made the right call when it came to Harper swinging on the third strike. But he wished that Hirschbeck had walked away from the incident.
"He is a good umpire. I like John," Johnson said. "He made the right call. What can I say? I wish he hadn't made it. I don't want to lose anybody. I definitely don't want to lose my three-hole hitter in the first inning."
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.