Micky van de Ven was forced off with what appeared to be a hamstring injury in the first half of Tottenham's Carabao Cup fourth-round tie against Manchester City.
The Dutch defender, who started the game at left-back, clutched the back of his leg after racing back to dispossess Savinho and looked in distress as he was replaced by Destiny Udogie.
Spurs were leading 1-0 at the time through Timo Werner's well-taken goal.
Van de Ven was visibly upset as he walked off the pitch and Yves Bissouma followed him down the tunnel to give him a hug.
He did reappear in the first half to sit on the Spurs bench.
But the injury is a major concern for Spurs, who face Aston Villa in the Premier League on Sunday.
Van de Ven was sidelined for two months of last season after suffering a hamstring injury at roughly the same stage of the campaign.
Spurs are already set to be without forward Wilson Odobert for a sustained period after head coach Ange Postecoglou revealed he had suffered a "serious" setback in his recovery from a hamstring injury this week.
City lost defender Manuel Akanji to an injury in the warm-up, with Ruben Dias taking his place in the side.
Both Postecoglou and Pep Guardiola have been critical of the schedule, with the City head coach saying before the game he would not "take a risk" with any of his fatigued stars in the Carabao Cup.
