It has been an impressive week for Atletico Madrid's Saul Niguez who has scored two goals in as many appearances this worldwide break, continuing to prove just how important he is in Luis Enrique's Spain.
It got worse for Croatia before the break as Asensio forced two memorable goals in the space of two minutes, first blasting beyond Kalinic from 25 yards before driving towards the box and curling a stunning effort that smacked the crossbar and went in off the unfortunate goalkeeper.
Spain scored three goals in each half as they completely outplayed Croatia, who were playing just their second game since the World Cup final.
With two wins from two and a goal difference of +7, Spain are firmly in charge of the three-team Nations League pool.
Asensio, who was not among the starters against England, also set up Rodrigo's goal early in the second half with a flawless through ball behind the defence. We had very good concentration.
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Celta Vigo striker Aspas replaced Diego Costa in the squad after the Atletico Madrid forward was released for personal reasons.
Croatia midfielder Ivan Rakitic wasn't too happy with his team's performance against Spain. Carvajal also provided the cross from which Saul headed the opener, giving Spain a huge injection of belief and rattling the visitors, who moments later conceded possession in midfield before Asensio smashed the loose ball home from long range.
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.
Belgium earned a comfortable win over Iceland thanks to a pair of goals by Romelu Lukaku and one from Eden Hazard. Spain was eliminated during the round of 16 of the World Cup, losing to Russian Federation on penalties after a 1-1 draw.
Spain, meanwhile, is coming off a 2-1 victory over England in its first Nations League match.