Cristiano Ronaldo was left on the bench for Erik ten Hag's first competitive game as Manchester United manager against Brighton on Sunday.
Ronaldo is reportedly keen to leave the Red Devils in the search for Champions League football.
The five-time Ballon d'Or winner missed United's pre-season tour of Asia and Australia, with the club giving him leave for family reasons.
Ronaldo did make his return last weekend for the first-half of a 1-1 friendly draw with Rayo Vallecano, but left Old Trafford before full-time.
Ten Hag described a number of players' decision not to stay until the end of the Rayo game as "unacceptable", but said there would be no further punishment.
Marcus Rashford looks set to step into Ronaldo's shoes up front against Brighton with Anthony Martial also ruled out by injury.
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Lisandro Martinez and Christian Eriksen are handed their United debuts from the start with another new signing Tyrell Malacia on the bench.