Complex sentence: A back injury led to him ending his career but after finding out that the injury was not as bad as first diagnosed, he returned to England when Stoke City signed him in 1960 he played ten league games for City during the 1960--61 season.
Split into simpler sentences: A back injury led to him ending his playing career, but after finding out that the injury was not as bad as first diagnosed, he signed for Stoke City in 1960. Younger played ten league games for City during the 1960--61 season.