West Ham wing-back Michael Antonio may be missing until January due to injury.
The 29-year-old underwent successful hamstring surgery on Tuesday on his right leg and is expected to be out for three to four months while he recovers.
He suffered the problem during the 2-0 Carabao Cup victory at Newport last week.
Manager Manuel Pellegrini has also now drafted in U23 player Xande Silva to his 25-man Premier League squad and he can play if needed this season.
Antonio, who is under contract at the West London club until 2021, played in West Ham's first three games of the season but missed the 2-0 win over Norwich at the weekend.