In the seventh inning, Span popped up to Starlin Castro for the second out. After the third out was made, Span went to get his glove and tried to stand up, and his back locked up on him.
"It never happened to me before. It scared the heck out of me," Span said after the game. "I'll take a few muscle relaxers on this train ride. Hopefully, it will loosen up. Good thing we have a day off tomorrow. I'll communicate with the trainers during tomorrow's day off and let them know how I'm feeling."
As for Espinosa, he has taken fly balls in the outfield during batting practice and the Nationals are confident he can play the outfield.
"I'm comfortable. I'm trying to get the job done and not overthink it," Espinosa said.
Espinosa didn't have any balls hit to him during his two innings in the outfield.
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the Time. He also can be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.