The 20-time English champions have signed Rasmus Hojlund this summer, but the Denmark international is yet to make his debut for the club due to a troublesome back issue.
Hojlund will again be missing for Saturday's Premier League clash with Nottingham Forest, which is likely to see Marcus Rashford continue through the middle.
Rashford has struggled in the team's opening two league games against Wolverhampton Wanderers and Tottenham Hotspur, while Anthony Martial cannot be relied upon to stay fit for an extended period.
There will also be no Mason Greenwood for the Red Devils, as the club have decided against bringing the youngster back into the fold following an internal investigation.
Man United continue to be linked with Fiorentina's Sofyan Amrabat, while there could be a left-back addition before the end of the transfer window due to Luke Shaw's injury.
The Red Devils are also believed to be looking to bring in another goalkeeper, with Dean Henderson potentially being allowed to move to Crystal Palace before next Friday's deadline.
According to La Gazzetta dello Sport, there could also be a forward addition, with Man United lining up an offer for Santos youngster Leonardo.
Roma continue to be heavily linked with the Brazilian, but it is being reported that the English giants are preparing to offer a £17m fixed fee with a further £4.2m in add-ons in a bid to secure his signature.
Leonardo, 20, came through the youth system at Santos, and he has represented the Brazilian giants on 151 occasions in all competitions, scoring 49 goals and registering 11 assists in the process.
This season, the forward has managed 16 goals and four assists in 32 appearances at club level, while he has another three years left to run on his contract.
Santos are currently 17th in Brazil's top flight and would be reluctant to let the attacker leave, but they are unlikely to be able to reject a sizeable bid from a team of Man United's standing.
Any incomings at Old Trafford in the latter stages of the window will largely depend on outgoings, though, with Eric Bailly, Scott McTominay, Harry Maguire and Donny van de Beek among the players being linked with exits.