Leoncelli was delisted from the senior list of Carlton and was offered a place on their supplementary list but found the club environment at Carlton overly focused on senior older more established players with junior development low on the clubs priority at that time.
He wrote David Parkin a letter saying he refused to believe he was finished at 19 years of age and to watch out for his return.
He built his game playing against the likes of Nicky Winmar, Peter Riccardi and Mark Ricciuto.
Since retiring from the AFL, he joined the Hamton Property Group as a development manager, and was a director of the Melbourne Football Club.
On the morning of 1 June 2017, Leoncelli was onboard Malaysia Airlines Flight 128 when it performed an emergency landing at Melbourne Airport due to a passenger claiming that they had a bomb on board and was going to blow up the plane.