AceShowbiz -

Alfonso Ribeiro, one of the frontrunners on "Dancing with the Stars", may have to quit the competition. The actor injured his back during rehearsal on Wednesday night, November 12 while he was trying to overcompensate for a groin injury which he sustained during his performance of The Carlton Dance in October, TMZ reports.

According to the site, Ribeiro skipped rehearsal on Thursday to get an MRI. Doctors reportedly say the next 48 hours are critical and he may not be able to perform on Monday night on the semifinals. An insider says to Us Weekly that producers are "worried he could cause long-term damage to his back."

A rep for the "Fresh Prince of Bel-Air" star says in a statement, "We can confirm Alfonso was injured during rehearsal. He is currently under medical evaluation. It has not been determined whether or not he will be able to perform on Monday."

Earlier this week, Alfonso told TV Guide that he's determined to make the finals despite having to deal with his groin injury. "There's three weeks left. There's three shows left. I've got two and a half weeks of dealing with this pain, and then I will absolutely have time to let this thing rest and recover," he said. "It'll be really nice once that happens, but hopefully I can stay on the show all the way to the end and make it to the final, and deliver a hopefully amazing performance on the finale."

Alfonso isn't the first contestant to suffer injury on "DWTS" this season. His pro dancer partner Witney Carson injured her back during rehearsal back in October, comedian Tommy Chong suffered a tear in his calf last week, and pro dancer Karina Smirnoff injured her wrist during a group rehearsal that forced her to sit out for a few weeks earlier this season.

"Dancing with the Stars" airs Mondays at 8 P.M. on ABC.