UPDATE: People reports that Mark Ballas will be sitting out this week's episode of Dancing with the Stars after injuring his back during camera blocking on Sunday. His partner, UFC fighter Paige VanZant, will dance with So You Think You Can Dance contestant and Dancing troupe member Alan Bersten.

The back injury is an old one for Ballas that he aggravated while preparing for the team's second week. There's no word on when or whether Ballas will return.

The original story is below:

Just two weeks into the season, Dancing with the Stars has already been hit with its first setback as performer Mark Ballas has injured his back during Sunday's blocking rehearsal, according to a report from People.

"He injured his back at camera blocking rehearsal on Sunday," a source told the outlet. "It's an old injury that he aggravated. It's up in the air if he'll be able to perform tonight."

In the meantime, Ballas' partner, Paige VanZant, is rehearsing with Alan Bersten, a former show contestant and current member of the DWTS dance troupe.