England were left to ponder their first competitive defeat at Wembley since they lost a Euro 2008 qualifier to Croatia in November 2007, a run stretching back 24 games - and also Southgate's first home defeat as manager.
Asked if this was a reality check for his side, Southgate said: "If anybody wasn't aware of it, then yes". "He scored a goal and he was in the penalty box more".
"It takes time. We've come a long way in a short space of time and today was as tough a test as you could have against a team that presses like that and are so good in possession".
Winning his first game in charge against England gives Luis Enrique a ideal start, and even with the recent retirements of Andres Iniesta, Gerard Pique and David Silva, he still has great quality to work with.
"We have got some players who can do it, others who are improving at it and for me it's the way I believe we should play".More news: Obama tells voters to step up or things can get worse
With Harry Kane continuing to lack the sharpness that has been his trademark over the years, the England coach is thinking of resting him for the friendly against Switzerland as much to give him a mental break as a physical one. It was a slightly different set-up to what he's usually accustomed to at Barcelona now because there was more of an emphasis on inviting the high press by circulating possession around the defence.
Most notable was Gomez's forward passing, with the Liverpool defender showcasing a rare ability, or perhaps willingness, to play vertically rather than horizontally. England have never lost more than three matches in a row throughout 146 years of worldwide football.
Spain were fluid and fluent throughout their first match under Luis Enrique and, after their shock World Cup last-16 exit to hosts Russian Federation ended a tumultuous campaign, will go confidently into their next game against Croatia, though a late foul by substitute Danny Welbeck meant they will not do so on the back of a draw.
"That's what I want, to reduce the space and press a lot and against a team with three defenders it was very hard", Luis Enrique said. I think he was a outcome of a unique talent.
Luis Enrique knows all about taking on a talented team that has performed well below its level, having lifted Barcelona from their post-Pep Guardiola slump to become Champions League winners again, so managing Spain will not faze the 48-year-old.