Question: The 1974–75 Seattle SuperSonics season included which former Boston Celtics center as head coach?
Sentence (from "1974–75 Seattle SuperSonics season"): In their second season with Bill Russell as head coach and with rookies comprising half the roster, the SuperSonics finished the regular season in 4th place in the Western Conference with a 43–39 record and reached the playoffs for the first time in franchise history.
Relevant evidence: Yes