And O'Brien may have unlocked the key to Graff later in life as he made a successful debut for the stable, taking out the Group Two Caulfield Sprint (1000m) to score his first win in over two years.
O'Brien explained he had bred Graff with Widden Stud proprietor Antony Thompson and they sold him as a yearling to Alan Bell for $200,000 at the Magic Millions Sales.
"I've known him since he was a foal, so it's good to be back involved with him and it's good to bring him back to winning form," O'Brien said.
"He's a horses that's always shown talent and raced at the top level throughout and hopefully this can give him a real confidence boost and we can get him back to winning another good race.
"Not that winning a Group Two on Caulfield Cup day is not a good race anyway."
O'Brien said he and jockey Damien Oliver hatched a plan where they would ride Graff quietly and then unleash his sprint and it worked to perfection.
Tough galloper Wild Planet continued Team Hawkes' successful Caulfield carnival with a narrow victory in the Group Three Moonga Stakes (1400m).
Co-trainer Wayne Hawkes paid homage to the horse's tenacity after his win.
"He's a pure racehorse. He's not the best horse ever but his will to win is amazing," Hawkes said.
Wild Planet was given a perfect ride from Hugh Bowman who settled him behind the leaders and managed to get him home in a photo.