As the defending Stanley Cup champions, the Bruins dominated the NHL in the 1970-71 season with a league-best 57-14-7 record, the Hart Trophy winner (Bobby Orr) and the top goal scorer (Phil Esposito, 76). It was one of the top three most talented Bruins teams ever.
This is why their first-round playoff exit at the hands of Canadiens rookie goaltender Ken Dryden was so surprising. Dryden had no prior postseason experience, but he played like a Hall of Famer in the seven-game series and made a plethora of unbelievable saves in each contest. After defeating the heavily favored Bruins, Dryden led the Canadiens to a Stanley Cup title a few weeks later.