Harry Kane will have a scan on Monday after twisting his ankle during Tottenham's FA Cup win over Millwall.
The Spurs forward rolled his right ankle under a challenge from Millwall's Jake Cooper in the early stages of his side's 6-0 quarter-final victory.
Kane did manage to walk off the pitch and down the tunnel unaided, but he was later seen leaving White Hart Lane on crutches and with his right foot in a protective boot.
Mauricio Pochettino afterwards said he fears the injury is similar to one which sidelined Kane for 10 games earlier this season.
"He twisted his ankle in the same way as before, it was the same ankle he injured in the game against Sunderland," Pochettino said. "Now we have to wait, we will assess it tomorrow.
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"It's difficult. We hope it's not a big issue but it looks a similar situation as his previous injury. We hope it's not a big issue. I'm sure it will be difficult to play against Southampton next weekend.
"Of course I'm sad about Harry's injury but we have to find a solution. When you lose a player like Harry you will miss him. Harry is one of the best strikers in England but we can't cry."
The injury will also concern Gareth Southgate as he prepares to name an England squad for the upcoming matches against Germany and Lithuania.
Kane has scored 24 goals in 28 appearances for Tottenham this season and is the Premier League's joint-top scorer alongside Everton forward Romelu Lukaku.