 Sullivan turned pro in 1992 and accumulated a 28-1-1 record with an International Boxing Federation intercontinental belt and wins over the likes of Garing Lane, Levi Billups, James Gaines, and Marion Wilson, setting up a bout with fellow rising prospect Hasim Rahman in 1997 on HBO.Sullivan held his own and lost a majority decision.After the loss to Rahman, Sullivan began 1998 by knocking out 33-1 Keith McKnight, but then would be stopped in the ninth round after a tough battle with undefeated contender Michael Grant.