The Germany international spent some of his early career with Everton, but failed to make the grade on Merseyside before being shipped out to Sampdoria in 2012.
Now 22, Mustafi has moved on to play for La Liga giants Valencia, and was a part of his nation’s successful World Cup in Brazil last year – making one start on the last-16 clash with Algeria.
He is currently rated as one of the best young defenders in Spanish football, which has alerted Spurs who are keen to give him another crack at Premier League life.
White Hart Lane boss Mauricio Pochettino is thought to be eyeing centre-back reinforcements, with the future of captain Younes Kaboul far from clear.
However, the Londoners are not short of competition for Mustafi, with Dortmund thought to be looking at him as a potential summer addition.