Chicago Cubs first baseman Anthony Rizzo will have his sprained right ankle immobilized in a boot for five to seven days and then will be evaluated, keeping open the possibility that he will play again this season.

Rizzo had to be helped off the field Sunday after turning his ankle while fielding a sacrifice bunt. He underwent an MRI on Monday that revealed a moderate lateral right ankle sprain, according to the team. X-rays on Sunday did not reveal a fracture.

"I have every intention of doing everything I can with the training staff to be back on the field with the boys," Rizzo told reporters before the Cubs-Reds game Monday night. "I think in a few days, really, will tell us a lot more."

Victor Caratini was in the lineup at first base Monday. Manager Joe Maddon said that Ian Happ, who replaced Rizzo Sunday, will also see time there.

Rizzo, who is known for charging hard on bunt attempts, broke toward the plate in the top of the third inning when Pirates pitcher Trevor Williams squared to bunt. As he neared the ball, Rizzo's foot appeared to dig into the turf and his right ankle turned.

After being tended to by a Cubs trainer and manager Joe Maddon, Rizzo was helped to the dugout, not putting much weight on the right foot.

"We're gonna miss Riz, we already miss Javy, but I really believe the rest of the group is up to the task,'' Maddon said, referring to Chicago's postseason pursuit already being hindered by a fractured-thumb injury to shortstop Javier Baez.

The Cubs hold the second wild card, one game ahead of the Brewers. They trail the Nationals by 1.5 games for the first wild card and the Cardinals by two games for the NL Central lead. They play St. Louis seven times down the stretch.

Cubs president Theo Epstein said the team will know more about its options for Rizzo once he is out of the walking boot.

"Once we get past that period of time then we can see if there are ways to manage the discomfort," Epstein said. "If there ways through taping to give him some stability to give him at least a chance to contribute in some way down the road.

"We're not shutting any doors but we're realistic that this was a legitimate injury that under ideal circumstances would take some time to heal."

Information from The Associated Press was used in this report.