It's not just "saving cap for Nikishin," it's having cap flexibility to make moves that keep us contending every year in the long run. Jake is 30 years old and got 8 years, sure cap may go up, it may not, who knows. But it's still a riskier contract. I'm not the biggest fan of his game and he got UFA $ at 30 on a long term deal that has a great chance of aging poorly. We've got lots of prospects and young players in the pipeline who could be hits and where we can allocate that cap space -- Blake, Morrow, Nikishin, Jarvis (already done but wasn't when we were trying to keep Jake), Nadeau, Artamanov, now Stank, etc. Investing big cap space long term makes sense for true core players hitting UFA (Aho, Slavin) and home grown guys we can get on bargain contracts in their prime years coming off ELCs or in RFA years. Also for premium positions (center, top pair defense).
Jarvis would certainly have been kept on a bridge deal had we signed Guentzel and then his long term contract would've been considerably more expensive. Necas would've been gone for considerably less return before the season. And I'm not even convinced we'd be that much better of a team right now with Guentzel on it. He's a fine player but I don't agree with many who think he's a game changer.
Yeah losing Necas definitely hurt our team this year and going forward. I would've been thrilled to trade him to CBJ for 5overall (Demidov), or for big game hunting for a guy we could keep, or even just keep him long term. He is a great player even in our system.
What we paid for Jake comes down to how you value those prospects. It wound up being a 2nd round pick (very late 2nd), Pono, Koivunen and Bunting (net zero as his play for the Canes was not great and cap hit high, and the Pens have now already moved him. honestly wouldn't be surprised to learn that other teams would've been asking us to give a pick for them to take Bunting).
As high as I was on Pono and Koivunen, they were extremely expendable and a 2nd rounder is also not really worth all that much to us. We actually got a 3rd back from Tampa just for his rights for that 8th year anyways. I don't think our overall package was worth that much more than a single 1st to be honest. Plus most of the deadline deals aren't exactly apples to apples -- not often a player in his prime like Guentzel is getting traded as a rental.