LaRoche has been dealing with back problems for at least a week, but the pain grew worse in his at-bat in the fifth inning. LaRoche was going to start taking medication starting Monday night.
"The last couple of days, it just got tighter late in the game, fourth or fifth inning. It was really tightening up just standing around," LaRoche said. "I've had it before. I hope it's quick -- a day or two -- but again, you never know. It's one spot in my lower back. It locks up and I'm able to get it pretty loose to get going. The further the game gets, the more standing out there at first on defense is what I feel the most. [Sunday against the Mariners], it was really sore, and today, the same thing."
During the current road trip, LaRoche is 1-for-23 and has seen his average drop to .257 for the season.
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.