Manchester United head coach Ruben Amorim says it is "impossible" to replace Bruno Fernandes as he faces up to a month without his captain.

Fernandes was forced out of Sunday's 2-1 defeat at Aston Villa with a hamstring problem, which Amorim said at the time would rule the Portugal midfielder out of Friday's visit to Newcastle (20:00 GMT).

Amorim refused to put a definitive timescale on Fernandes' absence when he spoke to the media on Wednesday, although he did say the expectation was that it is "not going to take a lot of time".

Sources have said privately they believe the 31-year-old will return for the Manchester derby with City at Old Trafford on 17 January, which would mean a five-match absence.

It is a huge blow at a time when key attackers Bryan Mbeumo and Amad Diallo are away at the Africa Cup of Nations, and Kobbie Mainoo, Fernandes' obvious replacement, is also missing with a calf injury.

"It is impossible to replace Bruno," said Amorim. "I said that this morning to the team.

"We need to take the good thing, if there is a good thing on that - a lot of people need to step up."

Fernandes has had a remarkable fitness record since his arrival from Sporting in January 2020.

In the intervening six years, he has only missed two games through injury and one more due to illness, meaning his current absence will be by far his longest during his time with the Old Trafford club, even if it is not as bad as initially feared, with a six-week absence.

"It is not just the creation," said Amorim. "At every set-piece he is the guy who is organising the team.

"He understands every position on the field, he pays attention to every detail. When you have a substitution, he is always the guy telling the other guys where they should be."

'I trust my players'

Amorim named Lisandro Martinez and Luke Shaw as two of the senior players who could step up, although it was Fernandes' fellow Portugal international Diogo Dalot who took the captain's armband at Villa Park.

After waiting all season for his chance, it is unfortunate for Mainoo that he is not able to step into Fernandes' shoes on the pitch, although Amorim says he expects the England international to return first.

With defenders Matthijs de Ligt and Harry Maguire still out and Noussair Mazraoui completing United's trio of Afcon representatives, Amorim will be without seven senior players against Newcastle - with only Casemiro returning after a one-match ban.

It is likely to mean more minutes for academy pair Jack Fletcher and Shea Lacey, who both made their senior debuts in the second half against Villa.

After repeatedly failing to take opportunities to push into the Champions League places, Amorim must now deliver results with a significantly weakened squad against opponents his side should beat, given that, after Newcastle, their next opponents are Wolves, Leeds and Burnley, who are all battling relegation.

The former Sporting coach remains bullish about their chances.

"I am confident we can win any game," he said. "Of course, we have some problems, but even without many players at the moment, I believe in the team and trust in my players. If we are really focused, we can win."