See below, but IF Vancouver is retaining half on Eriksson and his actual salary commitment is only $1m this year and $2m next year, and IF Buffalo is going to be short of the cap this year, then they're only taking on a small financial commitment to make this deal with no worries about cap hit.
Montour is an offensive D-man who didn't produce in Buffalo, so there's good reason why people are speculating whether he'd get a QO. I think he will, there's a bit of upside there, but he's probably worth a bit less than Virtanen.
The Sabres need a middle six power forward at RW, Virtanen suits them perfectly. A much better lineup fit than Montour. Throw in a 2nd and I think this is a good deal for Buffalo.
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IF OP means only a 33% retention on Eriksson then it's still an okay deal for Buffalo, but they can get better terms. There will be more clubs looking to unload cap hits then there are teams willing to take the other side of the deal. Vancouver should pay more.
To Buffalo:
Loui Eriksson (Van pays 20-21 bonus, $2m salary retained in 21-22)
Jake Virtanen
2021 2nd
To Vancouver:
Brandon Montour and 2021 4th, OR
Colin Miller and 2021 5th
Buffalo gets thirteenth forward and RW help.
Vancouver gets big cap relief and an NHL defenseman. Play him, trade him, sit him or send flowers.
Offer good only until QOs are due.
His total salary in 2021-22 is $4m, with a $6m cap hit. Correct me if I'm wrong but salary retention is a percentage that applies to both salary and caphit, so if you are retaining 50% of the salary, it's $2m, and you're also retaining a $3m cap hit (50%). Is that what you meant?