Harry Kane's season hangs in the balance with Mauricio Pochettino worried that the Tottenham striker suffered a 'similar' ankle injury to the one that saw him miss almost two months of this campaign.
"He twisted his ankle. Now we wait, assess and see what happened," Pochettino said.
"It is the same ankle as he injured against Sunderland.
"We hope it's not a big issue but it looks similar [to the injury earlier in the season]. It will be difficult for him to play against Southampton."
Spurs coped well in Kane's absence, with Son Heung-min scoring a hat-trick, while Christian Eriksen, Dele Alli and Vincent Janssen also struck.
The injury could also keep Kane out of England's forthcoming friendly against Germany and the World Cup qualifier against Lithuania in March.
Alli, who scored Tottenham's fourth goal in the rout, told BBC Sport: "It is always horrible to lose a player like Harry but when he went off everyone stepped up a gear.
"We wish him a speedy recovery. It was an important win for us not just in the cup but in the league as well, it is important to get the goals. We were hungry for goals."