Dancing With the Stars front-runner Alfonso Ribeiro may have to pull out of the competition because of a back injury, a source confirms to Us Weekly Credit: Adam Taylor/ABC via Getty Images

Alfonso Ribeiro's Dancing With the Stars dreams could be coming to an end. The Fresh Prince of Bel-Air star — a front-runner for the season 19 Mirrorball trophy — may have to pull out of the competition before the upcoming semifinals on Monday, Nov. 17, a source confirms to Us Weekly.

As first reported by TMZ, Ribeiro injured his back during rehearsals this week. Sources told the site he was trying to "over-compensate for a groin injury" he sustained during his performance of The Carlton Dance back in early October.

As of Friday morning, Nov. 14, the 43-year-old actor was still attending — but not participating in — rehearsals for his upcoming routine with pro partner Witney Carson. A source told Us he was watching Carson dance with a stand-in, and hoped to learn the steps visually. However, producers are "worried he could cause long-term damage to his back," the insider said. 

Ribeiro has not been at full strength since Oct. 6, when he and Carson performed his signature dance from The Fresh Prince. The routine earned a perfect score from the judges but left the star in excruciating pain. "I hurt my groin doing the Carlton," he shared two weeks later. "I think I did it so hard that I actually pulled it."

Despite that, Ribeiro continues to be one of the best dancers in the competition, and is consistently among the top-scoring couples week after week. He earned his second perfect score just a few days ago on Nov. 10, for a paso doble he and Carson did with fellow DWTS pro Lindsay Arnold to DJ Snake and Lil Jon's "Turn Down for What."

After the performance, judge Carrie Ann Inaba gave him a standing ovation, and Bruno Tonioli called it "the ride of the night."

If Ribeiro does end up leaving, the race for the Mirrorball will be down to four: Duck Dynasty's Sadie Robertson (and partner Mark Ballas), YouTube star Bethany Mota (and partner Derek Hough), comedian Tommy Chong (and partner Peta Murgatroyd), and Pretty Little Liars actress Janel Parrish (and partner Val Chmerkovskiy). 

Tell Us: Would you be sad to see Alfonso Ribeiro leave DWTS?