Tottenham Hotspur have confirmed Kyle Walker has undergone abdominal surgery but are unsure when the player will be able to return to action.
England international Walker has not played for Spurs since March and is facing a further lengthy absence after he was forced to go under the knife.
A statement from the club read: "Kyle Walker has undergone lower abdominal surgery. The England right back's pre-season preparations were disrupted by the abdominal injury and the decision to have surgery was taken following further medical assessment by specialist.
Spurs boss Mauricio Pochettino had hoped to avoid seeing his defender undergo the procedure but given his persistent struggles for fitness the club have now sought to address Walker's long term problem.
"Kyle is good some days. On other days he has a bad feeling," Pochettino said last month. "We believe he may recover soon but we need to be calm with him because it is an injury that he has had for five months."
Pochettino will also have to contend with a possible injury to Eric Dier. The 20-year-old, who has filled in at right back in Walker's absence, has withdrawn from the England Under-21 squad ahead of European Championship qualifiers against Lithuania and Moldova due to injury. The FA or Tottenham are yet to confirm the extent of the knock.
Dier, who signed from Sporting Lisbon this summer, enjoyed an impressive start to life at White Hart Lane, scoring two goals in his first two games while helping his side keep clean sheets against West Ham United and Queens Park Rangers.
However, the youngster was given a reality check last Sunday as his side lost 3-0 to Liverpool, with Dier conceding a penalty against Joe Allen that Steven Gerrard converted.
"It was very tough but we have to improve," Dier said.
"We didn't start the game too well and we paid for it with the early goal, but we've got to keep going.
"You can't take the highs too high and the lows too low, you've just got to learn from it and keep trying to improve – that's something we can strive for."