A neurologist's report on Monday will dictate whether the Irishman has a future in the sport after being out of boxing for almost two years.
The former World Boxing Organisation champion believes he had a black- out at the start of the sparring session with the British middleweight champion Howard Eastman, that led to him spending the night in a London hospital.
Collins underwent tests and a CAT scan, and said yesterday: "I didn't feel good going into the ring and I should have been honest with my trainer Jimmy Tibbs. I felt as though my head exploded, I felt dizzy, I needed a rest. I more or less went on the floor and I sat up in the ring and I felt light-headed. I was not taking any punishment and the session had only just started. In layman's terms you could call it a black-out.
"I don't believe it is serious, it could be a blip or a warning. A neurosurgeon read me my results and advised me what to do, and asked to see me again on Monday. He didn't say anything about boxing.
"The decision on my future is not mine, it depends on what the doctors say. When I know the facts then it will be my decision. Of course I'd love to box on. But this certainly got my attention. It's not happened to me before in boxing, but I've had headaches when I've not been boxing. I've got some questions to ask the neurosurgeon, which he was not in a position to answer earlier this week after the initial tests."
Whatever the conclusion of the neurosurgeon at Homerton Hospital, the British Boxing Board of Control would doubtless want to conduct their own tests before the Irishman fights again in this country.
Collins was due to have his comeback fight in Cardiff on 5 June, but that has been abandoned. Collins has not fought since stopping America's Craig Cummings in Glasgow in July 1997. That was a seventh defence of the WBO super-middleweight title he took from Chris Eubank more than two years earlier, and twice defended successfully against Nigel Benn.
The Scottish featherweight, Brian Carr, insists two successive British championship defeats will make him doubly determined to triumph when he attempts to win the World Boxing Union world featherweight title next month. He will challenge the South African, Cassius Baloyi, in Glasgow on 26 June.
"I am far more determined to win after two title defeats, I won everything in featherweight as an amateur, so I am comfortable at this weight. Baloyi seems to be good for the first few rounds, but then seems to die a death. I think I've shown I'm the better boxer," Carr said.Reuse content