I think Cassidy is better than most coaches.... but no fan base is 100% happy with their coach, at least, not after the first season. What I liked and didn't like...
I liked that he mixed up the lines. Putting Pasta with Marchand gave them a boost in the middle of the series, and I also liked that he recognized he needed to go back to the more spread out lineup for G5. I liked his willingness to put Wagner in the lineup. I even liked that he pulled Frederic and Grzelcyk. At the very least, it shows he's trying to push buttons and make something happen. I also liked our physicality this series. It felt like, for maybe the first time under Cassidy, that we were really hitting to hurt their better players, which I think you have to do in the playoffs.
I did not like how he deployed his forwards and D. He loads up the top D pair with Lindholm-McAvoy, doubles down by playing them primarily with the Bergeron line, and then gives them 70% Ozone starts. He's taking our 4 best defensive players (Lind, Mac, Berg, March) and deploys them exclusively in the offensive zone. On the flip side, he puts our 3 worst defensive forwards (Hall, Haula and Pasta) with Gryz/Reilly-Carlo on defense. So not only are we icing our least effective defensive forwards, that combination also puts our smallest/lightest Dmen in Gryz/Reilly, with our smallest center in Haula. Why not play that D pair with the Coyle line? Why not play them with the Bergeron line and let Mac and Lindholm play with Hall and Pasta? Cassidy made that Haula-Carlo combination the weakest 5on5 unit on the team and they were all big minus players in this series.
I also did not like that Cassidy didn't recognize that 5 man unit was a problem and didn't adjust. You could see the Haula line was getting caved in, yet he never put out a different defense with them. He also could have split Mac and Lindholm. He said he'd try that during the season but never did, and he didn't do it in this series either. Cassidy really loves to "load up" and put all his eggs in one basket and I'm just not a fan of the strategy, especially with the way he deploys them.
I also think Cassidy should take some of the blame for the PP. He runs it. It's his baby. Even when he was out with Covid, he was working with them in practice and prepping the PP for games via Zoom calls. So, there's some criticism there that he couldn't figure out how to get though the 4 man across the blue line strategy, and it's on the players for not executing as well.
All that said. This was a good season. This was a good series. And this is a good coach. He has an excellent record. I want no part of Sacco as head coach. Going forward, he has to find a balance between wins and development. I think he brushes off the lack of development onto Don Sweeney. When asked about working young players into the lineup he seems to always say that's a question for Donny, are we trying to win or are we trying to develop? That can't be the outlook going forward. They have precious little cap space and need to integrate young legs into the lineup.