Brendan had warned he could potentially be out for this week's live performance and now a rep for the 40-year-old has confirmed he has been told to rest by doctors.
According to Daily Mail, a spokesperson for Brendan confirmed the news and said: "He is resting on Doctors orders but everybody hopes the rest will enable a return to form for Brendan in next week's competition."
Their confirmation comes after Brendan recently revealed during an appearance on Strictly: It Takes Two that Anastacia has been practicing her routine with Gorka Marquez, another professional dancer on the show, in case he is unable to perform.
Gorka had been partnered with EastEnders actress Tameka Epson, who has since been eliminated from Strictly.
Brendan said: "I'll let you into a little secret. We have the lovely Gorka stepping in for me for a few days."
He then joked: "I don't know how happy I am about it, he's Spanish, he's good looking and has a body which is pretty much the best on the show... I kind of have the feeling it's going to go downhill for me from here."
His comments came after Brendan revealed he had taken himself to A&E in the early hours of last Saturday morning. He told fans on Twitter that he was having difficult breathing, but Strictly viewers saw Brendan later perform on the show that evening.
Brendan had shared a statement to his official website on Wednesday (19 October) and shared his hopes to be deemed well enough to perform this weekend.
He revealed he had been for further tests after being diagnosed with a chest infection and a decision on whether he can dance was being made today. Brendan told fans: "The doctor advised me to have complete rest... I am following his advice and the lovely Gorka Marquez is stepping into my dancing shoes to train with Anastacia whilst I am recovering.
"So far they are doing very well and continuing to train hard gearing up for Saturday. All being well I will be back on the dancefloor this weekend with Anastacia and we (with Gorka's brilliant help) can put in a great performance as if nothing has happened. Should I not be ready, Gorka and Anastacia will perform their quickstep with me cheering them on from Claudia's sofa or my own."
Brendan had tweeted he will update his statement following the decision. He hasn't yet commented on social media.
Strictly continues Saturday 22 October on BBC One.
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