Within minutes of the collapse, Collins, who has not boxed since July 1997, was taken to hospital where he received tests and a brain scan, which did not reveal any signs of ill health. The former world middle and super-middleweight champion was set to return to the ring next month after nearly two years on the sidelines.
However, his trainer, Jimmy Tibbs, said: "When Steve got himself together after they had done the tests and he had been given the all-clear, we all agreed that the best thing for him to do was to stop boxing.
"I was delighted when he told me that he wouldn't be boxing anymore. He said that he believed it was a warning for him and he needed that to make him stop boxing.
"He needed something like that to shock him into retirement. He's not skint and it's the right decision - Steve had said at the press conference for his comeback that he wasn't coming back for the money. To see a tough guy like Steve Collins collapsing to the canvas like that was very frightening."
Collins was due to contest a non-title bout on the supporting bill to Joe Calzaghe's World Boxing Organisation super-middleweight defence against Rick Thornberry in Cardiff on 5 June. He had then lined up an autumn meeting with the Welshman in an attempt to regain the world title, with the promise of fight against the World Boxing Council light-heavyweight champion, Roy Jones, if he won.
It is understood that Collins has returned home to Dublin where it is expected he will formally announce his retirement after a career in which he enjoyed epic victories over the likes of Nigel Benn and Chris Eubank. Collins won the WBO super-middleweight title in March 1995 by outpointing Eubank. He made seven successful defences, including a repeat victory over Eubank and two against Benn.
Eastman's trainer, Ronnie Davies, said: "I was terrified when I saw Steve falling forward on to the canvas. If there was a punch it couldn't have been that hard because we had told them to take it easy."