Not sure if anyone can answer this. Before I ask it , I want to point out something that I believe is accurate (correct me if I'm wrong)
If a player chooses to retire in the middle of his contract, the contractual obligation ends with both parties, but the team still hold his rights if he were come back during the lifetime of his contact.
So hypothetically what if Eichel retired and then does his own surgery. Once you retire, the team has 0 say on what surgical procedure you do in private life. Then after the surgery ,Eichel says he wants to return to the NHL . His contract with Buffalo will be counted again where it left off. Eichel resumes his former stance of wanting to be traded. I assume Buffalo can't suspend or even void his contract because his surgery took place at a time when he deassociated him self with NHL as a retired player.
It may be pointed out that if you retire, you need to stay retired for a full season. I don't think that's accurate. Mike Fisher once retired with Nashville, only to come back later in the same season and participated on their playoff run.
So can Eichel theoretically do what I suggest?