Tottenham fear they could be without key defender Jan Vertonghen for up to six weeks.
The Belgian has been ever-present in the Spurs side since his 2012 switch from Ajax.
However he picked up an ankle injury in the dying minutes of Tottenham's 2-1 win over Fulham last Wednesday, and was forced to miss the victory over Sunderland on Saturday.
According to the Guardian, his injury may be worse than initially feared, and could rule him out of the crucial festive period.
Tottenham are awaiting scan results on the injury this morning, but initial reports suggest it looks likely he will be missing for over a month, which will rule him out of key games against Liverpool this weekend and Manchester United next month, plus the FA Cup 3rd round tie against rivals Arsenal and the League Cup quarter-final against West Ham.
A provisional date for his return if the six weeks lay-off is confirmed could be Spurs' game against Manchester City at White Hart Lane at January 29.
The news will come as a huge blow for Spurs, who have come to rely on Vertonghen to act as cover at left-back with Danny Rose out injured.
Spurs look frail at the back with centre-back Vlad Chiriches also missing the 2-1 victory against Sunderland, with midfielder Etienne Capoue forced to fill in.
Youngster Kyle Naughton offered cover in Vertonghen's absence, although Rose was due to start training this week as he bids to return to full fitness. His return could be well-timed, although it is unlikely he'll be fit enough to feature against Liverpool on Sunday.
Spurs are currently also without Christian Eriksen, who picked up an ankle injury during the international break last month.