Romelu Lukaku did not travel with the rest of his teammate to face Bournemouth because of an injury.
Lukaku, 24, was absent from United’s line-up to face the Cherries in Saturday’s Premier League match after he suffered an unspecified injury in training on Friday afternoon.
Manager Jose Mourinho does not yet know the full extent of the problem and says the Belgium international will be evaluated in the next couple of days following the game at the Vitality Stadium.
“In training yesterday, after the press conference, he felt something that needs to be studied in the next couple of days”, Mourinho said ahead of the game.
“So Lukaku has not come and we decided to start with Alexis (Sanchez).”
Mourinho made one change to the side that beat Everton 2-1 at Old Trafford last Sunday, with Sanchez coming in for Marcus Rashford, who let go to the bench.
Club captain Antonio Valencia, Marouane Fellaini and Diogo Dalot all stay side-lined.