McMillan fought on, all fighters do, but he never regained what he so viciously lost that night in the summer of 1992 and after surgery was beaten in another world title fight by Cardiff's Steve Robinson. There was more surgery on the shoulder, this time a keyhole procedure in America, before a bloody and total end at York Hall, Bethnal Green, not far from his Barking home, in January 1997 when Paul Ingle stopped him after eight rounds. It was finally all over.
Three months ago McMillan returned to boxing when he took out a manager's licence and tomorrow night at the Bushfield Sports Centre, Peterborough, his first and only fighter, Terry Dunstan, meets Carl Thompson for the vacant British cruiserweight title.
"It was difficult to walk away," McMillan remembered. "Boxing had been my life for 17 years but the shoulder injury affected everything I did and I knew it was time to call it a day. My fighters will know the same thing."
There was a time at the start of the Nineties before the return of Frank Bruno and the arrival of Naseem Hamed when British boxing reached its lowest point in 50 years. Chris Eubank was the undisputed mouthpiece of a business in search of a star. McMillan entered the filthy fray at this point with a series of sparkling British and Commonwealth featherweight fights. He hit but was seldom hit back and was a sweet and long overdue reminder of boxing's cute past.
"Boxing is unexpected and it is impossible to take things for granted," McMillan said. "I seemed to have a lot going for me but I always treated every fight like it was my last. That is what makes boxing so unique."
In 1992 McMillan won the World Boxing Organisation featherweight title from Italy's Olympic gold medallist Maurizio Stecca. It was a brilliant performance and suddenly the sport and ITV had a player to market and consider but four months later Palacio, a perennial contender and noted hard man from Colombia, ruined McMillan's shoulder to end the false start.
The bad luck was not at an end and six months later Palacio tested positive for the HIV virus and was stripped of his title. McMillan had to endure a test for HIV because of a cut that Palacio sustained in their fight. McMillan was negative.
"As a manager I have the boxing experience that the boxers lack. I have seen it before and it is that experience that leads to respect and that is so important because I can't tell a boxer what to do, I can only recommend a move or a fight. The boxer has to make the decision," said McMillan, who was self-managed during his career.
It was not difficult for McMillan to agree terms for Dunstan to meet Thompson, a former WBO cruiserweight champion. It is an intriguing trade fight. The purse split is less than both boxers have received for similar fights in the past, but McMillan reached a deal with Golden Fists' Dave Lewis, who had been the fighter's conduit when McMillan boxed for Frank Warren. Another option involved a more lucrative European title fight for Dunstan in Moscow. "As manager I have to get the best money for the least danger," McMillan added. Moscow is dangerous.
As a fighter McMillan was always keen to keep his options open, which is not the operating practice of boxing's leading promoters and managers. Loyalty, a rare commodity between fighters and managers, is essential between promoters and TV companies and loyalty is unrealistic when fighters try to do deals with rival promoters.
During McMillan's brief flirtation with boxing fame he found himself in New York exploring the possibility of fighting for Don King. He was at King's office one day during negotiations to find a deal when King left the room. McMillan and an adviser never said a word, fearing a bug. In another room King was on the phone to McMillan's British promoter Warren, his partner, to check facts and figures. King and McMillan never did a deal and Warren promoted all of McMillan's major fights but their relationship was often angry and always edgy.
"I have seen the other side of boxing and the way the politics work," said McMillan, who is the secretary of the Professional Boxers' Association. "I can be the eyes for my boxers and guide them through areas they have never been."
Boxing is a business where flawed individuals begrudge anybody success and envy is worn like a badge of bloody courage, but McMillan has more friends than foes. If his fighter wins tomorrow night, which is not certain, McMillan will start to move up the current list of 159 managers. He will also start to lose friends and make enemies.