Christian Eriksen made his debut for the Red Devils in a false nine that failed to bring the team to life against Brighton, as Erik ten Hag lost his first game in charge.
If Ronaldo were to start today, then Eriksen falls back into midfield against his former employers to force one of Fred or Scott McTominay out of the starting XI.
Marcus Rashford also starts as transfer rumors around him continue to swirl with PSG enthusiasm.
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Ten Hag revealed that centre-back Victor Lindelof and striker Anthony Martial had injury doubts for the game. Facundo Pellistri, Brandon Williams and Phil Jones are also likely to miss, meanwhile.
Manchester United starting XI (4-2-3-1): De Gea; Dalot, Maguire, Martinez, Shaw; McTominay, Eriksen; Sancho, Fernandes, Rashford; Ronaldo.