After seeing only limited action as a rookie in 1962, Green was installed in the Cleveland backfield the following year alongside legendary Hall of Famer Jim Brown. He finished his first full season of action with 526 rushing yards, and also caught 28 passes out of the backfield. Even more importantly, he also helped open holes for Brown to gain a then-NFL record 1,863 yards. In 1964, the two helped the Browns capture their fourth NFL championship, capping the year with a stunning 27-0 shutout of the Baltimore Colts at the 1964 NFL Championship Game.