Cleveland Cavaliers
Biggest mistake: Not making a tangible addition to the roster
I'm sure if you ask most Cleveland Cavaliers fans, there won't be many who argue that this hasn't been a successful offseason. The biggest concerns for most Cavs fans heading into this summer revolved around getting a commitment from Donovan Mitchell. They scored on that front while also agreeing with Evan Mobley on a long-term extension. However, the Cavs haven't done much, if anything, to improve their supporting cast around their two stars. And with the way the likes of the Philadelphia 76ers and Milwaukee Bucks have improved on paper, that has to be at least somewhat concerning for Cleveland.
It's great that the Cavs were able to convince Mitchell to sign long-term. However, if the team doesn't improve coming off of last season, has the team really accomplished much this offseason? If the goal is an NBA Championship, there's still plenty of work for the front office to do.
There's a very real chance that Cleveland's inaction this offseason could end up being a huge mistake. Could we arrive at the midway point of the season with the Cavs being a 5th or 6th seed in the East? It could happen.