The 32-year-old has been a regular fixture for the Red Devils so far this season, with the 20-time English champions sitting 13th in the Premier League standings.
Casemiro has featured on 10 occasions in the top flight for Man United this term, starting seven of those matches and finding the net in the defeat to West Ham United.
The former Real Madrid man has also played a prominent role in the Red Devils reaching the quarter-finals of the EFL Cup, bagging a brace in the 5-2 smashing of Leicester City on October 30.
Since making the high-profile switch from Los Blancos to the Theatre of Dreams in August 2022, Casemiro has featured 99 times, scoring 15 goals and helping the club to FA Cup and EFL Cup glory.
Casemiro not part of Amorim's Man United plans?
According to BBC Sport via Spanish outlet SPORT, Man United's squad could be in line for some major changes during the upcoming January transfer window.
The report claims that the Red Devils are willing to get rid of a number of first-team stars during the mid-season trading point as they look to better their results.
It is understood that incoming head coach Amorim has informed Casemiro that he will be available for an exit from the club in the New Year.
Despite featuring in 10 of Man United's 11 Premier League matches so far in 2024-25, the Brazilian is supposedly set to depart Old Trafford.
It is also believed that Erik ten Hag signing Antony - who has failed to impress since his move from Ajax - will be able to leave the Red Devils in the near future.
Do Man United need to replace Casemiro?
With Casemiro heading towards a Theatre of Dreams exit, Man United are reportedly ramping up their efforts to secure a replacement in the New Year.
It has been stated recently that the Red Devils are interested in midfielder Martin Baturina, who currently plies his trade for Croatian powerhouses side Dinamo Zagreb.
Amorim's men are not alone in their interest of the promising youngster, though, with La Liga giants Barcelona also exploring the possibility of a move.