Manchester United said they had dealt with an "internal disciplinary matter" involving Marcus Rashford after he missed training last Friday and was absent from Sunday's FA Cup win against Newport County.
The Premier League club had said initially that the England forward, who was reportedly seen at nightspots in Belfast earlier in the week, was not well enough to be in the squad for the FA Cup match.
"He reported ill and the rest is an internal matter," manager Erik ten Hag told reporters on Sunday. "It is an internal matter. As I said, we will deal with it. I will deal with it."
United's later statement said Rashford had "taken responsibility for his actions", and the matter was now closed.
Rashford is back in training and available for United’s Premier League clash with Wolves on Thursday.
Ten Hag was unhappy with the England forward earlier this season after he was seen out celebrating his birthday just hours after a 3-0 defeat to rivals Manchester City.
Rashford has only scored four goals for United this season, after netting 30 in the previous campaign.