Spain rained on England's World Cup parade by coming from behind to win 2-1 at Wembley and give new coach Luis Enrique a winning start to the Nations League.
England were looking to seize on the momentum of reaching the World Cup semi-finals for the first time in 28 years and went in front early through Marcus Rashford.
However, Spain bounced back from their disappointing campaign in Russia thanks to goals from Saul Niguez and Rodrigo to show England still have some way to go to be considered one of the favourites for Euro 2020.
England's missing midfield
Exposed by the class of Croatia's Luka Modric and Ivan Rakitic when it came to the crunch in the World Cup semi-finals, England's inability to keep the ball under pressure was again exposed by Spain's own midfield maestros.
Southgate's preferred trio of Jordan Henderson, Jesse Lingard and Dele Alli offer plenty of energy and a goal threat, but couldn't compete with the exquisite technique of Isco, Thiago Alcantara, Saul or Sergio Busquets among Spain's array of talented ball players.
The England manager accepted his side were outplayed for large spells, but insists sticking by his principles to improve the Three Lions' play in possession is the only way to close the gap on the world's best.
"We can go back to an old style but we will never be a top team," warned Southgate. "We want to stick to the plan and get better at it."
Better call Saul
Enrique stressed the need for Spain to become more unpredictable after labouring to a last 16 exit at the World Cup to Russia on penalties despite enjoying 75 percent possession.
The inclusion of Saul at the expense of Atletico Madrid teammate Koke to help fill the void left by the retired Andres Iniesta and David Silva gave Spain the drive and penetration they lacked in Russia.
Despite a stellar record of scoring in the biggest games at club level, Saul was completely overlooked by interim coach Hierro at the World Cup.
And given the opportunity, he bagged his first international goal to halt England's momentum just seconds after Rashford opened the scoring.
De Gea's redemption
The chief culprit for Spain's chaotic World Cup campaign on and off the field, that began with coach Julen Lopetegui being sacked days before the tournament, for much of the Spanish press was goalkeeper David de Gea.
The Manchester United stopper made just one save in the entire tournament and was under pressure from Chelsea's Kepa Arrizabalaga, the world's most expensive goalkeeper, for his place as Spain's number one.
De Gea repaid Enrique's faith with three stunning saves to deny club teammate Rashford an equaliser.
However, he also needed the help of Dutch referee Danny Makkelie as he ruled out Danny Welbeck's goal deep into stoppage time for minimal contact between the two after De Gea spilled a looping clearance from Sergio Ramos.