Southgate rested a cluster of players who had been involved in wins against Tunisia and Panama in England´s opening two games in Russian Federation, including star striker Harry Kane.
But Martinez, who before the game had said winning was not a priority and made nine changes to his line-up, refused to look at the outcome that way and emphasised the vagaries of football.
It would have been even sweeter for England had Japan stuck to the script and won their last group game against Poland and topped their group. If Cahill gets a chance to play tonight then he will face a herculean task of keeping colleague Hazard quiet.
England and Belgium have already qualified from group G. Their clash will decide who finishes top and who finishes second. The winners of Group G are set to take on Japan; while the runners up face Colombia. The victor enters the side of the bracket that already features France, Brazil, Portugal, Argentina, Mexico and Uruguay, while the loser goes into the half with Spain, Croatia, Russia, Denmark, Sweden and Switzerland.
The scenario remains as many had predicted, but when the two sides meet at Kaliningrad Stadium tomorrow morning, the world will be watching for a different reason.
England manager Gareth Southgate and Belgium's Roberto Martinez rang the changes for their World Cup Group G decider in Kaliningrad on Thursday, giving squad players a chance to impress ahead of the knockout rounds.
What it highlighted, in bright lights, was the fallibility of playing for second place which, until late Wednesday, was expected to mean a quarter-final meeting with Germany or Brazil. That is the reality, we have put ourselves in this situation, we wanted to qualify and we have done that.
Were they to make it all the way through to the final, captain Harry Kane and his teammates would have four more matches to play. "We want to win".
"It's like any competition: The longer you stay in it, the less likely you're going to dodge any big teams". For me, we're delighted to be in the next round. We're looking forward to the atmosphere [at the game].
"When you're a leader and a manager, you have got to make decisions that are right for your group and are right for the primary objective", the Three Lions boss said.
"Myself and others we play with a lot of the Belgium players back home", Dier told reporters.
It was only Belgium's second ever win over England and their first since 1936 and coach Roberto Martinez suggested he was not anxious about the impact of the result on his team's possible future opponents.