Chelsea captain Reece James is are has suffered a fresh hamstring injury.
The England international was appointed as the club’s new skipper earlier this month following the summer departure of Cesar Azpilicueta.
Chelsea captain Reece James wore the armband last Sunday in the 1-1 draw against Liverpool but was taken off during the closing stages due to ‘tiredness’, according to manager Mauricio Pochettino.
Further tests, according to Sky Italy, have revealed a hamstring strain and Chelsea now face an anxious wait to discover the extent of the damage.
The 23-year-old was restricted to just 24 appearances last season and missed the World Cup after sustaining a knee injury during a Champions League win over Milan nearly 12 months ago.
James was replaced by Malo Gusto for the closing stages against Liverpool and the summer signing from Lyon is likely to deputise against West Ham on Sunday as Pochettino aims to secure a first competitive win of his tenure.
Chelsea, meanwhile, have reluctantly agreed to sell Lewis Hall after receiving a £28million offer from Newcastle.
The teenager made an eye-catching breakthrough last season and although the Blues had little intention of selling one of their brightest young talents at the start of the summer the bid, albeit from a Premier League rival, has been viewed as too good to turn down.
Pochettino has also encountered a setback to his hopes of signing Michael Olise from Crystal Palace with the highly rated winger having opted to sign a new four-year contract.
Chelsea activated the 21-year-old’s £35million release clause earlier this week and had been expecting to wrap up a deal quickly.
But Palace, angered by Chelsea’s approach, have convinced the former Reading star to commit his immediate future to the club and play a lead role in the post-Wilfried Zaha era at Selhurst Park.