Manchester United head coach Erik ten Hag has said that Casemiro is in "a race against the clock" to be available for Sunday's Premier League clash with Manchester City.
The midfielder missed out against Sheffield United in the league last weekend due to an injury which he had picked up while representing Brazil during the October fixtures.
Casemiro was back in training with the Red Devils earlier this week, but he was not involved against Copenhagen in the Champions League on Tuesday evening due to a European suspension.
The former Real Madrid midfielder was expected to start against Man City on Sunday, but Ten Hag said during his press conference that the 31-year-old remains a doubt.
However, there is some good news for the club on the injury front, with Aaron Wan-Bissaka now back in training.
"Aaron [Wan-Bissaka] was training today, Casa is a race against the clock, not 100%," Ten Hag told reporters when asked for a fitness update on Friday afternoon.
Wan-Bissaka has been absent with a hamstring problem since the middle of September, but the right-back could now be in contention for the Manchester derby this weekend.
Ten Hag also said that his side are now "going in the right direction" following three straight wins in all competitions, two of which have come in the league against Brentford and Sheffield United.
"That's definitely to see we are back where we wanted to be, this is a hard team to beat. They find a way to win, we're going in the right direction," he added.
"I think it's a match (Manchester derby) that is so huge because it's Manchester, it's internal, but it's also about world football. All the eyes will be on this game globally.
"I see positives and I see also negatives... we are not consistently in position at the level we can be where we show in games we can be, like Arsenal away and the first 20 minutes at Bayern [Munich] away.
"We should do this on a consistent basis, but pressing we're quite good, we have the most ball regains from the whole Premier League, the most middle regains in the whole league, our defending and pressing organisation, that is us.
"But we don't take benefit in the attacking transition moments, we have the ability in our teams to take benefits from it. This is how to grow and progress and the games will become more easy."
Man United have won five and lost four of their nine Premier League matches this season, with a total of 15 points leaving them eighth in the table, six points behind second-placed Man City.
