From the World Cup semi-finals to defeat in global football's version of the Intertoto Cup.
Shaw left the field on a stretcher wearing an oxygen mask and a neck brace after lengthy treatment but was "up and talking" in the change rooms.
Spain, who bowed out in the World Cup last-16 after a torrid campaign, nevertheless showed the benefits of a long-established identity and a level of creativity sorely lacking in England's midfield.
England and Spain will also face World Cup runners-up Croatia in League A Group 4 of the UEFA's new tournament created to add spice to the global calendar.
England team-mates expressed relief about Shaw's injury, with manager Gareth Southgate equally relieved.
England's joy was short-lived as La Roja hit back two minutes later, as Rodrigo surged into the box before picking out Saul Niguez, who sent a fine low strike past Jordan Pickford.
The match was halted for almost five minutes soon after the restart when England defender Shaw went down after a collision with Dani Carvajal and had to be stretchered off the field. However, the strike was ruled out for a foul on De Gea as Spain hung on to claim three points.
Challenging for the ball in the air with Dani Carvajal, the two players clashed, with Shaw coming off much worse and exhibiting the symptoms of being knocked unconscious.
England weathered the storm though and with Spain content to sit back, they pressed late on for an equaliser and should have had one when Welbeck rolled home after De Gea's fumble only to be harshly penalised for fouling the keeper.
"That balance with the left footer for us, with him and Danny (Rose), was an advantage in several situations".