The Irish-American investor enjoys a relatively low profile at the Stadium of Light, having slipped onto the club's hierarchy virtually unnoticed.
He has, however, been vital to the Black Cats cause this season, with his money helping to fund the arrival of several fresh faces.
Short is keen to remain in the shadows, though, with Quinn admitting his associate on the board is not one to court publicity.
Quinn told the Sunderland Echo: "Ellis Short's money was responsible for the three Spurs players, Ferdinand and McCartney coming to the club, as well as Djibril's loan fee.
"We were able to bring all of them in because of Ellis Short.
"The original Drumaville investors had the option of being bought out, of taking Ellis's money, but they said no. They wanted to dilute the shares so that his money could be used on players.
"So his money was vital.
Intelligent"Sunderland fans won't understand how much because he doesn't like publicity. And he has options to take more of a stake than he currently has over a period of time and that will again go on investment in players.
"He doesn't tell us what to do. He supports.
"But he likes to see us being intelligent and slick about our business and the disposal of some excess players was a help to us economically and also to the dressing room.
"The club has never had the sort of backing before that he is providing now and we will have it as long as we are showing ourselves to be a smart outfit."
Quinn also insists that Short is not using the club as a rich man's play-thing, ready to turn his back on the Wearsiders at the first sign of trouble.
"Football is his favourite sport, he's lived in this country quite a while now and his interest has escalated since he got involved with us," said the chairman.
"He's really committed, which is great but we have to prove to him that what he is committing himself to is more than sustainable.
"He's committed to making it a success."