In the bottom of the third inning, Rodriguez swung and missed at a Brad Bergesen pitch. Suddenly, Rodriguez left the batter's box and appeared to be in pain. The team's trainer and manager Jim Riggleman came to his aid, but Rodriguez told Riggleman that he was OK.
Rodriguez continued the at-bat and grounded out, but he left the game after the inning ended. He was replaced in the top of the fourth by catcher Wil Nieves.
Rodriguez is not expected to play in Sunday's game against Baltimore, and he hopes to be behind the plate by the time the Nationals play the Giants in San Francisco.
"I just have a little tight lower back. It wasn't anything like last time. It's just tight," Rodriguez said. "A tight lower back. It's going to feel like that for a few days. I guess I swung it too hard. It just got me a little bit. It's a little tight right now, but it's just going to take a few days. I'm sure, I'll be 100 percent. I will be OK in the next couple of days."
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.