Currently on-loan from Bayern Munich, Tel has had an inconsistent start with Spurs since his January arrival.
However, his former Rennes U19 coach Ferrer told the Mirror: "Mathys' first official match with the Stade Rennes academy was a Youth League match against Inter Milan.
"He was the youngest player, just 14 and there were players who were five years older than him. Despite all of that, he entered the match without fear with character and was immediately efficient, it was just so impressive.
"We realised that he was going to join a very big team and that Rennes was a springboard and a club that was going to become too small for him. This has since proven true, first with Bayern and now Tottenham."
Ferrer continued: "I have excellent memories of our collaboration, Mathys is a very respectful boy, you can feel a really good education from his family.
"He is hardworking, he had really high goals despite his young age and he did everything he could to achieve them.
"He showed great maturity despite his age, he was always very respectful and didn't hesitate to ask for advice. He was very attentive to the coaches' advice and constantly wanted to improve."