"Brazil are going to be very difficult to beat in a year's time," Vialli told BBC Sport. "They play like a team with the right spirit and the right tempo.
"They have handled the pressure very well - to play in Brazil is never an easy thing. They played with courage and were so aggressive. I know it has been a predictable, sometimes clueless, lethargic Spain, but that shouldn't take anything away from Brazil.
"It was a strange performance from Spain but I think they're going to give the senior players like Xavi and Andres Iniesta another year for the World Cup. The defeat is mainly down to their physical state. If you're not as sharp as your opponents, then you're going to lose."