Anthony Martial was ruled out of Manchester United's Sunday afternoon Premier League clash away at Southampton after falling ill.
The Manchester United forward travelled down to the south coast with the rest of the squad, but became ill overnight and was unable to play.
The Frenchman has not scored yet in the Premier League this season, only delivering one assist, although his general play has been strong.
Ole Gunnar Solskjaer revealed the reason for his absence at St Mary's and also explained his starting line-up.
He told the United website: 'Anthony fell ill overnight so he's in the hotel by himself, poor lad. So that's the reason Ant isn't playing.
'Edinson (Cavani) played well in midweek but we felt Mason (Greenwood) needed a game as well to start with.
'Donny (van de Beek) is definitely ready. He's been good in training and he has been good in games he's played, in the Champions League. It's never been Premier League or Champions League. It's to give him time to settle into the group.'
Dutchman van de Beek made his first Premier League start of the season after featuring regularly in the Champions League, while Mason Greenwood made a rare start up front.
But while one summer signing in van de Beek started, it was another new arrival who stole the headlines as Cavani scored two and set up another to help United complete a brilliant comeback from two goals down to beat Southampton 3-2 at St Mary's.
Midfielders Paul Pogba and Scott McTominay also missed the match after picking up minor knocks in the week.