As a 21-year-old, Ozil teamed up with the Portuguese at Real Madrid in 2010, joining the club for £10m from Bundesliga side Werder Bremen.
But despite his reputation as one of Europe’s emerging young talents, Ozil has admitted he was left paralysed by self-doubt ahead of his unveiling at Madrid.
In his new autobiography, Gunning for Greatness, Ozil explains how he saw himself as "a nobody" and questioned whether “this legendary team was still too big for me?”
But after consulting with Mourinho, the German reveals how the Real Madrid manager alleviated any previous concerns he had and encouraged him to grab hold of the opportunity on offer.
"Yes that's what I'll give you," Mourinho told Ozil. "A very real opportunity. Train hard. Then play. Show me you want it and I'll have you in my team. If you want to get better, I'll make you better.
"Real Madrid isn't too big a move for you. Real Madrid is the only right move. Trust me. I'll turn you into a regular player. And then all the doors will be open to you. You'll be able to show the world what you're capable of. And, believe me, that's a huge amount."
That persuaded Ozil - "an ambitious boy with a feeling for magic passes" according to Mourinho - to join the Spanish giants and "swept all my doubts away."
From there, the midfielder established himself as a firm fan favourite at the Bernabeu and went on to win one La Liga title with Real as well as the Copa del Ray.
Ozil later joined Arsenal in 2013 for £42.4m before lifting the World Cup with Germany in the summer of 2014.