Jonjo Shelvey could be unavailable for Newcastle United until late January.
Shelvey was dismissed in last night’s controversial 2-1 defeat to Nottingham Forest at the City Ground.
The midfielder was shown a red card for reacting to provocation from Henri Lansbury as he lay on the turf.
Paul Dummett was also sent off for the Championship leaders in first-half injury time.
Shelvey will be hit with an automatic three-game ban, and that suspension will take him up to a Football Association hearing later this month.
The 24-year-old has pleaded not guilty to a charge of misconduct dating back to September’s Championship defeat to Wolverhampton Wanderers at St James’s Park.
Shelvey is alleged to have used racially-aggravated language towards Romain Saiss during the fixture.
Newcastle will NOT appeal the red card shown to Shelvey against Forest, though Benitez has urged the football authorities to look at what he felt was play-acting from Lansbury.
But the loss of Shelvey for at least three games, and possibly eight or more if he is found guilty, could prove significant given his form for United.
Shelvey had been dictating the game against Forest until his dismissal.
“In the first half, we had the control of the game,” said boss Rafa Benitez.
“We were where we wanted to be, and we had one or two good situations.
“In general, the team was doing well and it was just a matter of time before they were making mistakes. But you cannot play with 11 players against nine and imagine that things will be different to how they were in the end.”
Ten-man United took the lead through Matt Ritchie before Dummett’s dismissal.
But a second-half strike from Nicklas Bendtner and an own goal from Jamaal Lascelles saw Forest claim all three points.
Newcastle manager Benitez was “proud” of his players, many of whom had played 120 minutes in Tuesday night’s EFL Cup defeat to Hull.
“The only thing I can do is praise my players,” said Benitez. “The way that they played, and their commitment and intensity was quite good in a very difficult situation.
“I will take the positives from that. The team was strong enough with nine players to compete against a team that is a good team. But, in these circumstances, it is almost impossible.
“I am really proud. I cannot change anything, but surely someone has to see the images and say that something was wrong.
“Someone has made a lot of mistakes, and they have to analyse whether that was the players or whatever.”