After the harum-scarum 3-2 win over Japan, it is hard to see how Martínez can set his team up in the same way when they face Brazil in their World Cup quarter-final on Friday

Roberto Martínez’s head must still have been spinning from a dramatic, wild finale to a game that finished with him stood on the pitch, in the Japan half, celebrating Nacer Chadli’s winning goal, yet everything was brought sharply into focus with the first question in the post-match press conference. “People will ask about the dangers of that system, with only three defenders, only two players in central midfield, so will you change that?” asked the reporter.

Calmly and politely, Martínez made the point that now is “not a day to speak about systems”. Maybe that was fair enough in the circumstances. It was close to midnight in Rostov-on-Don and Belgium had just become the first team in 48 years – since West Germany beat England in 1970 – to win a World Cup knockout match after being two goals behind. There was something to celebrate about that, even if Japan had taken Belgium to hell and back.

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For Martínez, who radiates positivity, the critical analysis could wait and was certainly not going to take place in an auditorium full of journalists. Reporters’ notepads would instead be filled with a long list of buzzwords – “desire”, “focus”, “personality”, “togetherness” and “never-say-die-attitude” – as the Spaniard praised his players for the fortitude they showed to recover from being 2-0 down with 21 minutes remaining.

The closest that Martínez came to any criticism of the Japan performance was when he reflected on an underwhelming opening 45 minutes and spoke about the players’ “fear of being able to fulfil the tag of being favourites of getting through to the next round”. The problems, in short, were mental rather than tactical. At least that was how Martínez wanted it to be seen.

Yet privately, if not publicly, the tactics board will need to come out soon at Belgium’s Moscow training base, because it is hard to see how Martínez can set his team up in the same way when they face Brazil in Kazan on Friday. It was alarming, for example, to see just how much space opened up on the flanks, in particular on the Belgium left, where Yannick Carrasco, the wing-back, struggled and Jan Vertonghen, the central defender stationed on that side of the pitch, ended up being badly exposed for Japan’s opening goal. Belgium also lost control of central midfield, where Kevin De Bruyne’s influence on the game was severely restricted until that wonderful 60-yard dash in injury-time that led to Chadli converting.

To give Martínez credit – something not everyone in Belgium seems keen to do – he made the changes that turned the game. Some will have wondered what the question could be for this golden generation of Belgium players if Marouane Fellaini and Chadli are the answer, but the final 25 minutes against Japan blew open the debate in that respect.

Yet the key decision for Martínez is what to do now. With Neymar et al up next, should he scrap the three-man central defence that leaves Belgium so vulnerable on the flanks? Is it time for Fellaini, with his physical presence, to come into central midfield? Would Belgium not be more effective if De Bruyne was allowed to release the handbrake and play further forward? Does Carrasco drop to the bench now? Could Chadli be relied upon defensively?

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Martínez, perhaps trying to relieve some of the pressure on himself as much as the players, made the Brazil game sound like something of a free hit for Belgium. “When you play against Brazil, you need to understand they are the best team in the competition, I think you have to accept that,” he said. He went onto question how many people would expect Belgium to go through to the semi-finals and, referencing the dreams that every young football-mad boy has when growing up, said that his players “can enjoy it from the first minute” against Brazil.

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Belgium, however, are not in Russia to enjoy the ride. Asked earlier in the tournament what would count as success, Thibaut Courtois replied: “Winning it, I think.” A glance through the starting lineup against Japan reveals that only two of the players – Carrasco and Romelu Lukaku – will still be in their 20s by the time the next World Cup comes around in Qatar. It is, in other words, now or never for this group of players.

Martínez needs to get it right from the start against Brazil to keep their dream alive.