Arsenal goalkeeper Manuel Almunia thought John Terry was 'dead' after the Chelsea captain had been knocked out in the Carling Cup final on Sunday.
Almunia was one of the closest players to the incident during the second half at the Millennium Stadium, when Abou Diaby accidentally kicked the England captain in the face during a goal-mouth scramble.
Terry was stretchered off with his neck in a brace, but after being taken to hospital, he was quickly released and returned to the ground to join in Chelsea's victory celebrations.
It was a positive ending to what at the time had looked a shocking incident.
Almunia said: 'When I saw him at first his eyes had rolled the other way and he looked like he was dead.
'I was very scared,' the Spaniard added, quoted on Arsenal's club website.
Meanwhile, Terry will be allowed to play in Saturday's Premiership clash with Portsmouth - as long as he is cleared to do so by a doctor.
It was thought the England skipper would be forced to sit out the match because of the Football Association regulations on players who suffer concussion.
Terry was knocked unconscious in a sickening accident in the Carling Cup final win over Arsenal, swallowing his tongue.
However, after being taken to hospital, he was quickly released and returned to the Millennium Stadium to join in the victory celebrations.
In a statement, the FA said: 'Following John Terry's injury in yesterday's League Cup Final, The FA can clarify that the rules on head injuries do not set down an automatic rest period for players suffering from concussion, but rather stipulate that each injury must be assessed individually by a doctor.
'The FA medical recommendations state that: `Since all head injuries are different in terms of the effects on the brain, no fixed time periods are applicable in professional football as to when the player should return to training and playing.
`The brain's response to the injury determines the time of return and playing and must be clinically assessed by the club medical officer or a specialist neurosurgeon/neurologist.
`The clinical rule is that no player should return to training or playing until symptom-free and sign-free at rest and on provocation.'
The statement added: 'The FA supplies clubs with a list of neurological specialists and units around the country.'