Tottenham boss Harry Redknapp admits Rafael van der Vaart is plagued by dodgy hamstrings.
Van der Vaart, 28, has grown increasingly frustrated at being subbed, with speculation linking him to a January switch to AC Milan.
But Redknapp told The Sun: "Rafa often comes off because he wants to. There is a weakness in his hamstrings.
"He runs himself ragged for much of the game but problems can occur when fatigue sets in and he gets too tired."