CHICAGO -- The Cubs know not to take any chances when first baseman Anthony Rizzo alerts the team that his back is flaring. One of those moments arrived on Saturday, when Rizzo exited during Chicago's 7-2 loss to the Nationals.

In the fifth inning at Wrigley Field, Rizzo left due to mid-back tightness and was replaced by pinch-hitter Jonathan Lucroy, who delivered an RBI double against Nationals starter Joe Ross. Lucroy remained in the game at catcher and Victor Caratini -- who had been behind the plate -- took over for Rizzo at first base.

The Cubs will have more information on Rizzo's status prior to Sunday's finale against Washington.

"[Head athletic trainer P.J. Mainville] came to me in the dugout and just told me where it got tight," Cubs manager Joe Maddon said after the loss. "That's all I have right now. I don't know enough yet. It happened so quickly. That's why, of course, Lucroy was just hanging out and I said, 'You're hitting,' and he goes up there and has a great at-bat. But there was no indicator that something was wrong."

Rizzo has dealt with back tightness at times throughout his career, including missing four games with a similar issue in May earlier this season. In 125 games this year, Rizzo has turned in a .290/.402/.526 slash line to go along with 25 home runs and 82 RBIs for the North Siders.