Tottenham boss Andre Villas-Boas admits they've lost fullback Benoit Assou-Ekotto for a month.
The Cameroon defender has barely missed a match in the last four seasons but he sat out Sunday's 3-1 win over Reading after a niggling injury flared up.
"Benoit has a small fragment in his knee that makes it swell a lot," Villas-Boas said.
"He has played through pain in the last couple of games. His knee may have to be washed up and if that happens we are looking at a four-week absence."