Possible Clues:

• Hoops star during the N.B.A.-A.B.A. merger
• The Sixers retired his number 6
• NBA slam-dunking great
• "Dr." with MVP awards
• 'Dr.' with MVP awards
• Cager Julius
• He wore 6 for the Sixers
• 1981 N.B.A. M.V.P.