Colin Shieff, consultant neuro-surgeon at the Royal Free Hospital in London, said he would normally advise similar injury victims to take it easy for at least two weeks.

Terry lost consciousness, swallowed his tongue and stopped breathing after a kick in the head from Arsenal's Abou Diaby during their 2-1 Carling Cup final win on Sunday.

Chelsea's captain checked out of hospital after treatment and returned to the Millennium Stadium in time to join in the celebrations with his victorious team-mates.

The influential Chelsea defender could now make a swift return against Portsmouth on Saturday.

But renowned brain expert Shieff told PA Sport: "Someone who came in to us with a similar story and which was witnessed by so many, I would suggest to them that they take it easy for a couple of weeks.

"Boxers who were rendered unconscious would not be allowed to go back into the ring until they had satisfied the requirements of the regulatory authority. The boxing board of control would not let them fight for two or three months afterwards.

"It is one thing feeling well enough to get back to the team and another to being considered fit to play. He is more than likely to have had a brain scan on Sunday and it would probably have showed up normal and that there was no bleeding.

"During the period a person is knocked out, the brain is not working. It is like having a computer which suddenly doesn't work and won't accept anything you type or which refuses to save anything. When you get it working again, you might find it has saved your document but it may not have.

"During the period he was out, his brain wasn't getting a lot of oxygen but Chelsea are concerned about the guy as well as his performance and I am positive they will have obtained some neurological opinion and given him an MRI scan to determine whether there is any other damage.

"You can't always predict these things and it may take a while to get right. But generally, if someone is feeling fine in 24 hours, then there is likely to be no long-term problems."

But the good news for Terry is that if he plays at the weekend and gets another blow to the head, Shieff insists it will not be a danger to the Chelsea defender.

"It will be classed as a completely new event," explained Shieff. "It will not accumulate into being a greater risk. It is not likely there will be any additional damage from playing a week later but there maybe a concern that his performance might not be as good as it should be.

"But if there was any suggestion he was not right, then they would have to take him off straight away."