West Ham United boss Sam Allardyce fears Enner Valencia's head has been turned.

The striker has been linked with Chelsea since the New Year.

Allardyce said: "I think [the speculation] affects you without doubt, subconsciously. I don't think he generally goes around thinking it has affected him as no player ever tells you that they are playing badly.

"But, subconsciously, it has to have an effect as you are not absolutely certain about your future.

"I think that there has definitely some thought that goes on subconsciously in terms of, 'Where am I going to be next year? Should I stay here or should I not? Should I go somewhere else? Or I am just looking after myself as it [the deal] is already done?'"