The Brighton goalkeeper has enjoyed a meteoric rise from League One to the Premier League within the past year.
He dislodged Mathew Ryan, who is now on loan at Arsenal, as the Seagulls No.1 stopper earlier this season.
Sanchez's performances have attracted attention from international level as the Mail claim England attempted to convince him to play for the Three Lions instead of Spain.
But the 23-year-old stayed loyal to his homeland and could play in one of their World Cup qualifiers against Greece, Georgia and Kosovo later this month.
He will battle Manchester United's David de Gea and Athletic Bilbao's Unai Simon for a starting place.
Sanchez, born in Spanish city Cartagena, moved to England when he was 15 and had failed to earn any international acknowledgement until earlier this week.
Brighton boss Graham Potter was thrilled by Sanchez's Spain call-up.
He said: "I am very pleased for him, I am very pleased for [goalkeeping coaches] Ben [Roberts] and Casper [Ankergren] who have worked with him and all the guys in the academy.
"It is a great story, we are delighted of course as a club and it is a reward for Rob for his work with us and his development since he has been with us and everybody connected with the club that has helped with that."
With Jordan Pickford sidelined with abdominal muscle injury, England's upcoming World Cup qualifying matches against San Marino, Albania and Poland present a chance for Nick Pope or Dean Henderson to stake a claim for the No.1 spot.
Southgate also handed a maiden call-up to West Brom goalkeeper Sam Johnstone.
Robert Sanchez reportedly turned down the chance to play for England before receiving a first-ever Spain call-up this week.