Manchester United defender Chris Smalling is running out of time to prove his fitness ahead of the trip to Tottenham on Sunday, sources have told ESPN FC.
The centre-back trained away from the main group at the Nad Al Sheba Sport Complex in Dubai on Tuesday as he continued his recovery from a foot injury.
Smalling has missed the last six games but caretaker manager Ole Gunnar Solskjaer had hoped to have the 29-year-old available at Wembley.
Marcos Rojo is also injured and Eric Bailly is suspended which could leave Victor Lindelof and Phil Jones as the only available centre-backs against Tottenham.
Smalling has returned to light training but would have to come through a session with the rest of the squad unscathed before being considered to face Spurs.
United will return from their warm weather training camp in Dubai on Thursday.
They are set to given the day off on Friday before returning to training at Carrington on Saturday to go through the final preparations for the clash against Mauricio Pochettino's side.
United are hopeful Paul Pogba will be fit enough to play at Wembley after the midfielder missed the FA Cup win over Reading through injury.
Pogba, who was on the end of a heavy challenge from Jonjo Shelvey during the 2-0 win over Newcastle on Jan. 2, stayed behind in Manchester for extra treatment while the squad flew to Dubai on Saturday evening.
He joined up with the group on Monday and was able to take part in training on Tuesday.