MADRID • Hat-trick hero Isco may be getting no love under coach Zinedine Zidane at Real Madrid but, for country, the midfielder looks set to play a key part in Russia as Spain rammed home their credentials as one of the World Cup favourites.

Isco scored his first career treble as La Roja annihilated Argentina, who were without Lionel Messi, 6-1 in a friendly at Atletico Madrid's Wanda Metropolitano on Tuesday.

The 25-year-old, who has become one of the first names on coach Julen Lopetegui's team sheet, is expected to start at the June 14-July 15 World Cup in a front three alongside Diego Costa and David Silva.

And he revealed after the match that it was a relief to play for the national side as Zidane had no faith in him unlike Lopetegui.

"He gives me confidence with minutes, with games," Isco said. "With Madrid, I do not have the confidence that a player needs."

He signed a five-year contract with Real last September, but there would be no shortage of suitors should he decide his future lies elsewhere, with English Premier League clubs Manchester City and Tottenham rumoured to be interested in his services.

"When you don't play a leading role or have continuity in your club team, the games with the national team give me life," added Isco, who Zidane has often benched in favour of Marco Asensio and Lucas Vazquez this season.

"I have the confidence of the coach here (with Spain), I still have a lot of enthusiasm to work, to improve, to be a starter for my club and in the national team."

It was a good night too for Costa, who passed his audition to be Spain's lead striker with flying colours after scoring the opener.

The Atletico man had been left out by Lopetegui as his move from Chelsea was ratified only in January owing to his club's transfer window ban. But he now appears to be in pole position up front, ahead of Rodrigo Moreno, Iago Aspas and Alvaro Morata.

"I went six months without playing but I knew that if I started playing again, I would have a chance of returning," he said.

Aspas, the leading Spanish scorer this term with 16 league goals for Celta Vigo, did his own selection chances no harm by coming on to score one in a flurry of second-half goals as the hosts netted with all six of their shots on target to extend their unbeaten run to 18 games.

Thiago Alcantara made it four shortly before the hour after Nicolas Otamendi headed in a consolation earlier for Argentina, who suffered their heaviest defeat since a 2009 loss by the same score to Bolivia.

Messi's hamstring strain meant the South Americans were without their talisman and after a poor qualifying campaign, Jorge Sampaoli's side have now lost two of their last three games, conceding 10 goals in the process.

The Barcelona great had been looking on from the stands but with 10 minutes remaining, he left his seat, having seen enough as his hapless team were humiliated.

"They've really given us a slap in the face," said a crestfallen Sampaoli afterwards.

"I feel bad for the boys... we didn't have balance or solidity and we were all at sea.

"We have to take responsibility and take another look at who will make the final list."

Argentina's major dailies tore into the La Albiceleste, with La Nacion calling the rout a "real punch in the face".

Former international forward Jorge Valdano told Spanish radio station Onda Cero that Messi is "the only reason that anyone is even giving Argentina a sliver of hope of winning the World Cup".

AGENCE FRANCE-PRESSE, XINHUA