After topping Group H without catching fire, Spain made a statement in winning their first World Cup knockout match since 2010 as beat Austria 3-0 in the round of 32.
Luis de la Fuente's side will face with Portugal or Croatia on July 6 in Dallas, Texas.
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Having come into the tournament as favourites, Spain disappointed early as they played out a goalless draw with the island nation of Cape Verde before improving to comfortably see off Saudi Arabia and Uruguay.
All eyes were on Spain's star-studded forward line that fired them to European Championship glory two years ago, but it's their defence that has impressed so far with Luis de la Fuente's team yet to concede a goal at the tournament.
Part of Spain's lack of attacking inspiration has been down to the Lamine Yamal's lack of fitness as he continues to build himself up full fitness after a hamstring issue.
Excluding penalty shoot-out losses, La Roja are on a 35-match unbeaten run in all competitions, equalling the national record set by the legendary Spain team that ruled international football from the late 2000s to the early 2010s.
In keeping that run going, they got the better of an Austria side that qualified for the round of 32 by the skin of their teeth owing to Algeria's extraordinary 3-3 draw with Senegal that allowed Ralf Rangnick's team to cling on to second spot in Group J.
Lamine Yamal and Co. will find out their next opponent when Portugal face Croatia at midnight BST.