Well, it's very hard to project that as we don't know the specifics of who is available, etc. But my foot print is pretty simple.
1. Goalie. Likely via trade. It's hard to project out who is available at this point. I'm calling Calgary and seeing if Vladar will be available since Wolf had a strong season, Montreal with Allen, Washington with Vanacek/Samsonov, NYI with Varlomov, Seattle with Drieger, heck LA with Quick. No stone unturned in getting this resolved before the UFA market hits. Priority 1.
2. Defense. The UFA market actually is reasonably strong here. Ideally I'd like to add 2. Obviously I don't think we are realistic players for Letang/Klingburg/Manson. Subban could make some sense given his brother likes it here. A 2-3 year, mid dollar deal could make sense. If Schultz is ok on a 1 year deal that could work. I really like paying a little over market if we could get Cole on a 2 year deal, he's my idealized best fit after Manson, but I think Manson is unrealistic. On the trade front, Dumba could make some sense. I think your big priority is adding at least 1 vet who is a steady, reliable guy who can play in his own zone and help the PK.
3. A competent, two way center who can help with faceoffs and the PK while contributing about 40-50+ points reliably. While the UFA market is reasonably strong here (Copp, Kadri, Trocheck and to a lessor extent, Paul) the trade route probably makes more sense. Though, paying to get a players rights and signing them would be fine. I'd love to solve this issue via trade, I simply haven't heard any names on the market that are a fit at this point.
Overall, this isn't time to swing for the fences or go all in. But is should be time for reasonable aggression. I'm not moving the top pick, but I'd be OK moving 2 out of next 3 picks (this year) if I can solve 2 of the issues I listed above.
We all want to improve the team for next season, but look at some of the names your listed.
Goalies: none of those names are going to get the team very far. Jake Allen in 31, has never been a true 1A goalie. Montreal might move him to create space, but he's not pushing the team far. Washington isn't moving Samsonov, and Vanecek hasn't proven anything yet. Varlamov has a 16 team NTC, he's not coming. Drieger isn't the answer, and Quick would just be a mentor type. Holtby is a good mentor type but he's not carrying any team. Kuemper and Husso showed they aren't that type of goalie either. Campbell could be but at age 30, he's not coming to Buffalo.
I can see why Adams is considering Anderson coming back. Because aside from Campbell signing, the rest of the goalies who could come don't move the needle much, and with UPL he might be better off looking for a mentor type goalie.
Defenseman: Klingberg isn't coming to Buffalo when there are plenty of other teams a lot closer to a Cup. Manson isn't coming; his family and ability to win are going to drive where he goes next. Schultz is 31 and probably wants to go to a contender. Maybe Subban comes but he's 33 and looking at reduced role and minutes going forward. Ian Cole would be a solid pick up. Dumba could also be a good trade.
Forwards: so when I dial up the "competent two way center" machine, I also get Trocheck and Kadri. Trocheck is 28 and knows where he signs next likely determines if he wins a Cup. Kadri is 31 and he's in the same boat. It would take an overpayment, and a contract that looks like an albatross in the later years, to get Kadri. Andrew Copp might be a good signing, but he's not a top 6 center, and for what Buffal would use him for, they can get a bottom 6 center for less. Maybe Chris Tierney works.
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No one that I'm seeing fits the three criteria: cost, desire to come, fits the role needed. Maybe you get Ian Cole to come fill in on the third pairing. Maybe we get Johan Larsson to come back as the 4C.
Buffalo can go try to work things out with some of the bigger names. But there are better teams with cap space who are going to get those players (Klingberg, Kadri, Trocheck). Buffalo's best bet is to be patient, let the kids continue to improve the team from within, and add only when it makes sense.
The Sabres are 1-2 years away from thinking about big UFA moves.