Spain coach Luis de la Fuente praised Lamine Yamal's performance in the 1-0 win over Portugal on Monday, which secured qualification for the knockout stages of the World Cup, describing it as one of the best displays in the 18-year-old's career.

Substitute Mikel Merino scored the winner in the first minute of second-half stoppage time in the match played in Arlington, sending Spain to the quarterfinals for the first time since winning their only World Cup title in 2010.

De la Fuente said: "For me, Lamine played one of the most important matches of his life. Whether he was brilliant or not, for me it was one of those matches that will help him grow more than others."

Yamal arrived at the World Cup with a nagging hamstring injury and started on the bench in the goalless draw against Cape Verde.

He then returned to the starting lineup and scored once in the 4-0 win over Saudi Arabia.

In the match against Portugal, the Barcelona forward registered three shots on target, helping Spain maintain pressure before Merino's decisive goal in the dying seconds.

De la Fuente noted that the physical effort exerted by defenders trying to stop Yamal may have contributed to Portuguese defender Nuno Mendes' injury in the 56th minute, forcing him off the field to be replaced by Nélson Semedo.

De la Fuente said: "Lamine delivered an amazing performance. He put in a great effort for the team and defended. When he had the ball, he always instilled fear in the opponent. He instilled a lot of fear in them."

He added: "We still need Lamine in this World Cup to continue developing and to deliver such performances."

Spain will face the winner of the round of 16 match between the United States and Belgium in the quarterfinals.

When asked about the potential quarterfinal opponent, De la Fuente said his focus remains on Spain's progress.

He added: "Any opponent you face at this stage will have done enough to deserve to be there, and whoever the next opponent is, it will be a bigger challenge than those we have faced so far."