It isn't? I'd say it's a very, very good reason to hold a grudge. If they force him to play for $1.5M, they're treating him like a rented mule for as far as any of us can see, no good reason. Any other QB in a contract year that went to the SB two consecutive years would be renegotiated, the only reason he is not it because of the size of the salary jump. Absolute bare minimum, they should renegotiate the last year of his contract for a 10x raise.
I fully reserve the right to change my position if it turns out he's being a tool, which is maybe not out of the question.
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Imagine for a moment a world without hypothetical situations...
Chances are, he is being just as unreasonable as they are at this point, and he may even want to hit the FA market to see what his value really is. But even if their offers have been ridiculously low, he really has a small number of teams that are landing spots for him. The universe consists of 32, and probably half are not interested for one reason or another. I know it only takes one, but as his agent I would advise him not to alienate any one of them, because you never know which one it is that will really pay the most when the contract rolls in.
A year from now he will have more money than he ever dreamed possible, and what he does or doesn't get this year won't mean a heck of a lot.
I'm not sure if you wrote that thinking you wre agreeing or disagreeing with me; but I think we do agree. Someone will pay him for sure, but you never know which team would go the highest. He only has 32 potential NFL jobs, and not all of the teams are looking for, want to pay, or are able to pay a QB contract such as he will demand. The Packers won't. The Colts won't. The Lions won't. Etc. So, there are a very limited number of teams that will be in the bidding for his services. Since you never know which team will pay the most, and/or if one will pay noticeably more than another; it does him no good to hold a grudge against Seattle.