Back tightness has Nats' LaRoche day to day

LOS ANGELES -- Nationals first baseman Adam LaRoche left Monday night's 6-4 victory over the Dodgers in the top of the seventh inning because of lower back tightness and was replaced by Kevin Frandsen.

Manager Matt Williams has ruled out LaRoche for Tuesday against left-hander Clayton Kereshaw.

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.