Pro dancer and fan favorite Peta Murgatroyd -- who was already preparing for the upcoming season after recently concluding a three-month DWTS live tour -- had to back out unexpectedly due to medical complications.
Peta spoke with Peopleon Monday, explaining that her orthopedic surgeon recently informed her that she required an operation that would bar her from dancing for six to eight weeks.
Peta had already begun rehearsing for the new season with her partner, singer Andy Grammer. However, Peta said she could tell "something was not right" while the two started preparing.
"I got my MRI results back and it was a really bad diagnosis," the 29-year-old pro dancer explained. "It showed I had four torn ligaments and a floating piece of bone at the back of my ankle. My doctor said I needed surgery and I knew I needed to put my health first if I want to keep dancing on the show into my 30s."
Peta's surgery is currently scheduled for surgery in mid-September.
While Peta will not be able to dance with Andy during the season, she does plan on sitting in during rehearsals to help out however she can.
Andy's new partner has yet to be announced, but is set to be revealed on Wednesday's Good Morning America.
Peta joined DWTS in 2011 as a troupe member and joined the cast of pros during season 13. She's participated every season since signing on, and even took home the mirror ball trophy in season 14.
"I'm just looking forward to being back on my feet as soon as possible and being a part of the show again," Peta said. "It's super frustrating but I'm going to fine and I'm going to be back in week eight or nine of the show."
Another familiar face that fans will miss is long-time judge Len Goodman, who won't be returning for season 21 due to a scheduling conflict with the U.K. show Strictly Come Dancing, where Len is also a judge, and the birth of his grandson.
Bindi Irwin was the first DWTS season 21 contestant to be announced. Check out the video below to hear how excited she is to participate on the competition show, which kicks off Sept. 14.