For the opening 45 minutes, it seemed fair to wonder if much had changed from Euro 2016, when Marc Wilmots' tactics were torn apart and he was jettisoned, to be replaced by Martinez. Panama may have tried to kick Belgium, and Eden Hazard in particular, off the park but their opponents' physicality was no excuse for Belgium's shortcomings.
Before he finally got the sort of delivery he craves to score twice, Lukaku must have felt he had been transported back to Old Trafford in December, when Manchester United lost the derby 2-1.
Belgium were crying out for Yannick Carrasco or Thomas Meunier to cut inside from their wing-back positions to assist Kevin De Bruyne and help create some numerical supremacy in the middle. Instead, they were rigid and it suited a limited Panama. Martinez felt his team were too anxious to impress and that edginess certainly led to some errant passing but he also complained the grass was too long and dry.
"It was the first game and we wanted to be perfect," he said. "We need to grow and take the lessons into the next game."
Panama were rough and ready and racked up five bookings in less than an hour.
The game was screaming out for some quality and Mertens obliged within two minutes of the restart. His cross had been only partially headed clear by Roman Torres, leaving Fidel Escobar and Hazard to challenge for the ball. It popped up and Mertens had only one intention, cracking a superb volley into the far corner.
A Panama goal may have thrown the cat among the pigeons. As it was, Belgium began to exert more control and eventually eased clear with another two goals. For the first, Hazard passed to De Bruyne, whose lovely cross with the outside of his right boot found Lukaku, who stooped to head home.
De Bruyne also instigated the third before Hazard surged forward and slipped in Lukaku as Panama's defence advanced, with the United striker dinking a lovely finish over keeper Jaime Penedo. Now that is service he can do something tangible with.