Opening the show, Claudia Winkleman told viewers: "Now, you may have noticed that Will and Janette are missing from tonight's line-up. Unfortunately Will suffered a knee injury in training and although he was desperate to take part tonight, after a full medical check he's been told he absolutely cannot perform and must rest."
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Will and his partner Janette Manrara had been set to perform a jive to Casper by Little Richard.
But Strictly confirmed: "Under the rules of Strictly Come Dancing, Will has been granted a bye to next week."
The Paralympic star had jumped off a table during practice, but landed on a straight leg. Explaining the injury in a recording from home, Will said he'd initially thought he had broken his leg and was left in intense pain. Medics said he would not be able to dance on Saturday night.
Will, who is a gold medal-winning Paralympian, has the condition Arthrogryposis which affects all four of his limbs.
Tess Daly said: "Will, I know you'll be watching at home so we all wish you a speedy recovery."
And while the rules of Strictly will allow the couple to return next week, it is not clear how long Will could need to recover.
"Fingers crossed he comes back next week," Janette said, while Will added in a tweet: "I'll be back."
Will Bayley is not the first Strictly contestant to be granted a "bye" through to the next week. In 2016, Laura Whitmore was given a "bye" in week five after injuring her ankle during training. Previously, Natalie Gumede was also given a "bye" in week seven of 2013 when she fainted during the dress rehearsal and missed out on performing in the live show.
American singer Anastacia was also unable to compete in the dance-off in 2016 because of an ankle injury she'd sustained during her Saturday night performance. The result was instead decided based on the competitor with the highest number of audience votes, allowing Anastacia to stay in the competition.
And Will Bayley not the only one missing from the show this Halloween Week – as Alex Scott's partner Neil Jones also suffered an injury, leaving Kevin Clifton to step up and learn the routine in "about 45 minutes."
"You may have also noticed that Neil is missing this evening," Claudia told viewers. "Now, unfortunately he also suffered an injury earlier today and is unable to dance tonight, but the brilliant Kevin will be stepping in."
Kevin's own partner, Anneka Rice, has already been knocked out earlier in this year's show.
Neil tweeted that he was "gutted" to miss the show but that Alex is in "safe hands" for her street/commercial Ghostbusters Halloween routine.