However, Spain struck back nearly immediately, with Saul firing in the equaliser two minutes later before Rodrigo took advantage of a static England defence to poke in following a free-kick, earning a 2-1 win.
"Spain pressed us and we didn't keep the ball well enough", he said.
'Marcus Rashford had a great impact on the game. This time it was different. "He knows we have real belief in him", Southgate said. "He scored a goal and he was in the penalty box more".
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.
"What we did to promote comfort on the ball was start to get players who are comfortable on the ball".
England take on Switzerland in an International Friendly on Tuesday night at the King Power Stadium, live on Sky Sports Main Event.
Hospitals bombed as Idlib families flee regime offensive
The problem is if they try to flee to Turkey they will find a closed border and risk being shot if they try to cross illegally. They seized the territories, with the backing of the U.S-led coalition, after chasing out Islamic State militants.
"As the game wore on, we started to work that out and I thought Eric (Dier) provided some stability for us, and him and John (Stones) being able to rotate positions allowed us to play through midfield better". They need - having come away for 10 days - football.
"I think at the moment we have to stick with the plan, stick with what we're doing and just get better at doing it".
Rashford's opener, following an 11th-minute Luke Shaw cross, hinted at a performance and result that would extend the team's post-Russia honeymoon period. England have never lost more than three matches in a row throughout 146 years of global football.
Thanks to the high pressing of Spain at Wembley these forays forward were seriously curtailed with both time and space being at a premium. We have to go through those experiences, otherwise we would go into a finals tournament in two years' time and, if we were just playing qualifiers now against lower standard opposition, we might have a perception of where we are, which would be false. "Everyone can see it should be a goal". "If anybody wasn't aware of it, then yes", he said. "But I don't think we were under any illusions, as a coaching team".
"Look at those who have gone and those that come into the team".
"It was hard but we had good spells in the game and we probably created the better chances". When we are match fitter we will function better up the pitch.