I didn't verify this but... On Twitter I saw where Mike Lupica posted a statement quoting Bob Ryan about Bill Russell. "In his final 14 years as a basketball player, Bill Russell's team participated in 21 winner-take-all contests (nine NCAA tournament games, one Olympic gold medal game, 10 Game 7s, one deciding Game 5), and Bill Russell's team won all 21."
If that is true, it is quite impressive...