Yet even a year ago such a development would not have been contemplated. While several English club sides had experimented defensively, none had dared introduce a flexible system. The thought of entrusting players - defenders at that - with decision-making was inconceivable. The national side had remained rooted to tradition - it was the one part of the team Terry Venables did not tinker with in his first 18 months. He had only changed the personnel through injury. When available, the back four was Rob Jones, Adams, Gary Pallister and Graeme Le Saux. At least, went the cry, he's got the defence sorted out.
But he was only just beginning. At the World Cup Venables had seen how the preference for split-strikers, one up front, one tucked in behind, had caused problems by making defenders uncertain whether to go with their man and leave the space behind, or mark the space but leave the man. He had then adopted a similar practice, playing Teddy Sheringham off Alan Shearer. But, while he had begun to set the puzzle, he had yet to solve it when posed by other teams.
Faced with such a dilemma most English defenders mark space - they do not feel comfortable in midfield where their ball control lets them down. But that means the team becomes outnumbered in midfield. As the match against Romania illustrated, good sides, allowed a man spare, can make England chase shadows for long periods. The domestic solution, adopted by teams like Aston Villa and Liverpool, was to play an extra central defender and push the full-backs up, making five in midfield. But this made the side top-heavy with defenders, and still left them square at the back.
When played in Europe the third defender is a sweeper, or libero, who provides cover for the markers and adds a dimension when pushing up. This option was not available to Venables: there was no such player available in the English Premiership.
Enlightenment was at hand. It came first from Don Howe, the FA's technical co-ordinator and an assistant to Venables. He went to look at the Ajax system and came back brimming with ideas. About the same time,Venables encountered Louis van Gaal, the Ajax coach, on a coaching seminar in America.
"They play a central defender with two full-backs," said Howe in China this week. "We thought we could do the same. We began talking to the players about it, in team meetings and in conversation. We began working on it in training, doing very hard sessions. I would take them and we would do 15-30 minutes, then we would swap the defenders around and go again, three times a session. It was hard, physically and mentally."
Venables began encouraging his central defenders to step out. Steve Howey did so against Colombia, but with no great confidence. Four matches later Gareth Southgate came in against Bulgaria. He stepped out a bit but it was his full debut and he was wary of over-committing. So it came to Croatia, and the great leap forwards. The onus was on the flanking defenders, Gary Neville and Stuart Pearce.
"You need the right personnel," said Howe. "Gary Neville was ideal because he had played centre-back and full-back. Stuart had more adapting to do; we worked hard with him and it was not a problem for him."
"It is not always easy to change things with older players," added Venables after the team had arrived in Hong Kong. "They can be set in their ways; they have been successful with the old system and want to keep it. You need players who are open to new ideas. The bonus is if you can get older players like Adams and Pearce on board, they will lead other players."
Adams has been portrayed for so long as the archetypal English defender, strong in the air, tough in the tackle, slow on the turn and worrying on the ball, that his ability to adapt has been questioned. This is forgetting how accomplished he was as a teenager with Arsenal before he became identified with sterility and offside traps.
Adams himself has no doubts. "You put labels on people but I feel comfortable in this system. I am delighted that the manager has the brains and the knowledge of the game to do it.
"If the opposition do not play three-up, why have we got four back? Years ago we had the four of us just standing there - now I say 'Off you go Gareth, go in and force the issue up front'." Southgate nearly did so in dramatic fashion on Thursday, bursting forward from a defensive four to shoot over early on.
"I think it is a positive way of playing three at the back," Gary Neville said. "You only have three defenders with two wingers coming back. It is about the discipline of knowing your own job and communication. It was very noisy on Thursday, but that helps in a way. You keep in eye contact more and you have to rely on your ability to defend well rather than rely on shouts.
"Playing in a three suits me more than playing full-back or centre-back," Neville added. "I have played both positions from a young age but this one allows me to get forward a little bit, without having the onus to go forward and support attacks all the time, and it allows me to defend as well."
Howe realises the system has yet to be truly tested. "We will only find out how good it is when we play an Italy or a Germany. No one else does it except Ajax, but we could lead the way. Clubs often follow the national team - if they are successful." The easing in of Adams and Phil Neville - who was sent into the stands last Saturday for the Hungary game to watch the system - probably justifies the Asian trip, as long as there are no complications with Gascoigne's blood poisoning, no one is injured today, and there is no hooliganism.