While there was never any doubt about the quality of a squad overflowing with individual talent, questions centred on whether there was a steely mettle to match.
Elimination by Wales in the European Championship quarter-finals two years ago suggested that, for all the star performers, the collective could be quite fragile, an impression confirmed by the first hour in Rostov-on-Don on Monday when they were tactically outsmarted by Japan.
But a double change in the 65th minute allowed Belgium to change gears and forge a remarkable comeback from two goals down to win 3-2 and book a quarter-final meeting with Brazil on Friday -- avoiding being on the wrong end of what would have been one of the great World Cup upsets.
Bringing on Nacer Chadli and Marouane Fellaini was the obvious thing to do and, while no coaching masterstroke, emphasised the resources at Roberto Martinez's disposal.
The pair drove Belgium to the last-gasp win with Chadli fittingly grabbing the winner with virtually the last kick of the match.
Belgium almost had to unshackle themselves after Japan had laid out a simple but sharply executed game plan.
A high press made it near impossible for the Belgians to play the ball out of defence and Kevin De Bruyne, sitting just in front of the back three, was so harried that he was hardly able to touch the ball. This made the supply forwards erratic, unsettling the whole team.
Their plan to employ two flying wing backs was quickly thwarted as they were sucked back into position by Japan's repeated long diagonal balls to the flanks.
The Japanese had clearly done their homework and, enhanced by some sharp passing and energetic play, made Belgium look underwhelming.
But once the two substitutes were on, De Bruyne was freed to thrust forward, eventually offering Belgium the speed in the build-up which, combined with their physical superiority, allowed them to eventually bulldoze their way to victory.
But what they needed most was fortitude and there were moments after Japan had gone 2-0 ahead when signs of cracks suggested another Belgian flop.
By digging deep, and finding a steely side, they now must believe have a real chance to go on and beat Brazil and head into the final week of the tournament.
(Reporting by Mark Gleeson in Nizhny Novgorod; Editing by Neil Robinson)
