Amazing Race All-Stars Amazing Race All-Stars

Eleven teams are set to take to the starting line again on The Amazing Race All-Stars (Sunday, 8/7c, CBS) — key word being "set."

For the first time, one team will be prohibited from going on the Race. "After a thorough examination, our doctor determined that one team is not capable of going because of a medical concern that we had about one team member," host Phil Keoghan tells TVGuide.com. "The emotion at the start of this Race is unlike any that we've ever had before. I have to break the news to everyone else. It's obviously devastating and affects not only that team and the other teams, who realize that suddenly there's this major change. This is absolutely the most dramatic thing that's ever happened. It's gut-wrenching. It broadsided us."

Photos: Meet The Amazing Race All-Stars cast

Exclusive: Brendon and Rachel "so excited" to return for Amazing Race All-Stars

18 TV shows based on movies