Ramos understands why the defender joined Spurs and Madrid already have Mendy and Marcelo at left-back.
Speaking to Radio Marca, Sergio Ramos said: "For now it [left-back] is a very populated position with Ferland Mendy and Marcelo.
"And if they [the club] have made a decision to let Sergio Reguilon go it's because they received a good amount of money for him.
"Reguilon had less chance of minutes with Real Madrid than the other two and I think he will adapt well to Spurs. He is a player with a lot of potentials."
Mendy will be Zinedine Zidane's first-choice left-back this season with Marcelo providing cover for the Frenchman.
Reguilon, who joined Tottenham on a permanent deal for a fee in the region of €27 million, can return to the Bernabeu thanks to a buy-back clause in his contract.
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