Sir Alex Ferguson has confirmed midfielder Anderson has joined the list of injury concerns for Manchester United's game against Sunderland on Saturday.
Anderson was replaced 10 minutes before the end of United's 2-0 victory over Otelul Galati in the UEFA Champions League on Wednesday and could miss the weekend's Premier League fixture with the Black Cats.
The Brazilian's injury concern could provide Ferguson with more selection problems after Wayne Rooney was used in an unfamiliar central midfield role against Galati.
Michael Carrick and Darren Fletcher both sat out that game, while Tom Cleverley will not be risked this weekend due to an ankle problem.
Ryan Giggs is also carrying an injury and is joined on the sidelines by Ashley Young and Chris Smalling, although Nemanja Vidic will return against Steve Bruce's side after sitting out the European win through suspension.
"Vidic will be back but maybe Anderson is the one player who picked up an injury last night," said the United manager. "We'll see what he's like. He could be doubtful.
"There will be no returns for Young, Smalling or Cleverley though."
Ferguson is also awaiting the results of a scan on Michael Owen after the striker suffered a thigh injury during the early stages of Wednesday night's success.
He added: "It's a killer for him. He started the season well, he's been training terrifically. His two performances in the League Cup have been great.
"I hope he's not out for too long. We've assessed him this morning, he's had a scan but we don't have any results from that yet."