World Cup runners-up Croatia were humbled on their return to competitive football as a revitalised Spain ran out 6-0 winners at the Estadio Martinez Valero this evening.
Spain were in dreamland two minutes later as Asensio cheekily lofted a shot from 20 yards that ricocheted off the crossbar, before deflecting in off goalkeeper Lovre Kalinic for the third goal.
Croatia, for whom Ivan Rakitic was making his 100th appearance, rarely got to grips with their opponents and conceded three times more in the second half through Rodrigo Moreno, Sergio Ramos and Isco.
Rodrigo scored after slipping past the Croatian backline on a through-ball from Asensio in the 49th minute.
Spain and Croatia go head to head in England's group, and World Cup bronze medallists Belgium get their UEFA Nations League campaign underway, all live on Sky Sports on Tuesday night. "It was really good playing here", he said after the game. Gylfi Sigurdsson had an early shot deflected as Iceland pressed forward, but once Belgium had taken a decisive 2-0 lead, the hosts struggled to create anything resembling a decent shot on goal.
Luis Enrique couldn't have asked for a much better start as coach of Spain's national team.
A somewhat surprise starter given Iago Aspas' showing against England, Asensio repaid his coach with arguably the finest performance of his career.
Although this was a night on which a new generation of worldwide stars were born, Sergio Ramos was not to be left out as the defender lost his marker from a corner to head home his fourth goal of the season on 57 minutes.
Croatia meet the Three Lions in a repeat of the World Cup semi-final on October 12 in Rijeka.