Chelsea captain John Terry is undergoing a ''precautionary scan'' on his right foot after taking a knock in training today.

The news comes as a blow for Chelsea's preparations as they attempt to win the double when they face Portsmouth in Saturday's FA Cup final and if it proves to be a more serious problem, his participation in the World Cup could be in doubt.

A statement from the club said: ''John Terry has today taken a knock in training and has gone to hospital for a precautionary scan on his right foot.

''He left Cobham walking freely in a protective boot, and we await the results which are expected on Thursday.''

It also gives England coach Fabio Capello a headache as he prepares for the World Cup in South Africa and the Italian will undoubtedly be monitoring the situation carefully.