‘Hall wore 4 during his junior career with Windsor of the Ontario Hockey League and kept the number through his first six NHL seasons with the Edmonton Oilers. He switched to No. 9 after joining the New Jersey Devils, where 4 was retired for Hall-of-Fame defenseman Scott Stevens, then wore No. 91 during his stint with the Arizona Coyotes last season.’
Hall to wear No. 4 with Sabres
Source: Sabres.com