Spain's thrashing of Argentina in Madrid on Tuesday could be a "dangerous" result for the World Cup hopefuls, according to Ernesto Valverde.
Isco struck a hat-trick in a 6-1 demolition of the Lionel Messi-less visitors at Atletico Madrid's Wanda Metropolitano home, with Diego Costa, Thiago Alcantara and Iago Aspas also on target.
Spain coach Julen Lopetegui cautioned after extending his unbeaten run in charge to 18 matches that a friendly victory means nothing for his side's World Cup hopes.
And Barcelona coach Valverde agrees with Lopetegui, noting over-confidence could be a problem for 2010 winners Spain after they dismissed Argentina so easily.