Jack Sullivan, son of West Ham United chairman David Sullivan, has confirmed that defender Winston Reid has picked up a hamstring injury.
The 27-year-old reportedly picked up a knock in training, and Sullivan has suggested that Reid will be out of action for four to six weeks.
Reid - who signed a new six-year contract at Upton Park earlier this year - was absent for a month earlier this season, and Sullivan told Hammers fans on Twitter that the New Zealand international will be unavailable for the Christmas period.
Very bad news... Reid Injured in training 4-6 weeks with hamstring. But some players will return faster than anticipated due to hard work
— Jack Sullivan (@jsullivanwhu) December 9, 2015
Reid could miss West Ham's fixture against Stoke City on Saturday afternoon.