Complex sentence: From 1985 until 1989, Sather retained the title of head coach but split coaching duties with John Muckler, winning the Jack Adams Trophy in 1985--86 as the NHL's coach of the year.
Split into simpler sentences: From 1985 until 1989, Sather split coaching duties with John Muckler, but retained the title of head coach. Sather won the Jack Adams Trophy in 1985--86 as the NHL's coach of the year.