Hall, Everton's former academy chief, was responsible for developing Osman during his youth.
"People talk about Leon having made his debut 10 years ago. No he didn't - he made his debut for Everton 20 years ago for our Under-11s," Hall told evertonfc.com.
"He's been here longer than almost every other member of staff. That says something about the kind of quality and character of the man. Everton has been his club, still is his club and will always be his club."