He's not going to suck. He won't be worth 8M in all likelihood, but if Nashville can absorb the cap hit, then it doesn't matter. Tampa can't afford to do that and we've been playing Moneyball for years due to serious cap constraints.
Also think Nashville agreed to overpay in order to get his pedigree. He's been the best captain in the league by all accounts, is a Stanley Cup winner, and his work ethic is top notch. They want him to mentor the younger guys and he's great at that.
McDonagh when he got traded back called Stamkos first thing and when he talked to Stammer, both Stamkos and Kucherov were working on-ice drills a week after getting bounced in the playoffs. That is the culture established in Tampa and I'm sure a culture Trotz would love to see instilled in Nashville.
It's wrong for him to be wearing that jersey though so when these 4 years are up, Stamkos needs to come on back home and take up a position in the front office. Whether BriseBois is still there or not remains to be seen.
After this PR nightmare with the Tampa fanbase, it's quite possible BriseBois' office chair is getting a little warm if this roster shake-up doesn't pan out, along with his recent trade blunders past 2 seasons (this summer being the exception, but those trades were to fix his previous mistakes).