Tottenham boss Mauricio Pochettino showed serious concern over what looked like a "very bad" ankle injury to Jan Vertonghen against West Brom.
The centre-back limped off during a 4-0 thrashing of the Baggies that fired Spurs into second in the Premier League.
Vertonghen departed White Hart Lane on crutches and Pochettino confirmed the club will assess him immediately in the hope he has not sustained ligament damage.
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He said: "It looks very bad. We feel very disappointed. But we need to wait a little bit. Tomorrow and Monday we will assess him better. It’s swollen, the ankle."
Vertonghen lunged for the ball by the touchline after an hour of play and landed awkwardly on the join, appearing to roll it before crumpling to the ground in pain.
As he immediately assisted by Tottenham medical staff, but the Belgian 29-year-old was forced to head straight down the tunnel for treatment and had to be carried.
He was visibly upset as chants of 'Super Jan Vertonghen' rang around White Hart Lane and was soon replaced by Ben Davies.
Pochettino will now be desperate for a more positive analysis when the injury is further investigated with a crucial trip to Manchester City coming up next Saturday.
Vertonghen has played in every Premier League match this season, apart from the 4-1 win at Watford when he was suspended after picking up five yellow cards.