The answer is tough to say. Although Bruce Cassidy has had an impressive stint so far in his six seasons with the club, are some of his good fortunes due to luck?
Cassidy has a record of 245-108-46 over his 399 games behind the Bruins' bench, which is good for a points percentage of .672. Unfortunately, his postseason record is just .500 at 33-33.
Back to the luck part. Was Cassidy just the beneficiary of inheriting an already elite team in the Boston Bruins? Maybe, but to coach a team to a points percentage higher than .650 in every season as bench boss is more than just good luck.
That's precisely what Cassidy has accomplished with a 2021-22 record of 51-26-5 for a points percentage of .652. Cassidy broke his own record of five straight seasons of a points percentage of .650 or higher to start a tenure with an NHL team, making it his sixth straight.
In NHL history, there are 112 coaches who have coached six or more seasons.
Three out of 112 have had six consecutive years (not to start a tenure) with a .650 points percentage or higher:
Scotty Bowman, Montreal Canadiens: 1975-1980
Glen Sather, Edmonton Oilers: 1982-1987
Bruce Cassidy, Boston Bruins: 2017-2022
(Jon Cooper, Tampa Bay Lightning, currently at five: 2018-2022)
The only and very substantial difference? Stanley Cup Championships.
Scotty Bowman made the playoffs eight of eight seasons with the Canadiens and won the Stanley Cup in all five opportunities he had.
Glen Slather made the playoffs in 10 of his 11 seasons in the NHL (three seasons in the WHA) with the Edmonton Oilers and won the Stanley Cup four times while losing in the final once.
Bruce Cassidy has only made it past the second round once. In 2019 when the Bruins lost to the St. Louis Blues in seven games in the Stanley Cup Final. A good argument for Cassidy is the difficulty to win nowadays.
The dynasty days of the NHL died in the 1990s when the salary cap era took over.
Cassidy deserves a lot of the credit for the Boston Bruins' successful seasons as of late, but sometimes a Stanley Cup is the only judge of success.