I'm not sure that's accurate.
No one was expressed any known concerns about his health related to this injury, and Yzerman said that he could play if they wanted/needed him to. They're protecting him for the playoff run.
I do not believe, nor have I heard any report, any murmur, anywhere that this injury impacted his sale price.
His value was what it was guys.
It's negotiating 101 to point out anything negative that can give you leverage to a better deal.
Yzerman also had more leverage in the negotiation because of the fact that he didn't absolutely need to make the deal, but the Rangers did.
McDonagh being injured only could have helped Yzerman in the negotiations because he's an asset that can't be used right now, and has been injured a majority of this season (hence why his play was so poor).
We don't know many details about the injury, but it's obviously something worthy enough that if he didn't have the proper time to heal, could be nagging even during playoff time.
If McDonagh was 100% healthy, and playing at a high level, the ball would be in Gorton's court from a leverage perspective in what he wanted to demand. That could have very well been more than what we got.
But, we will never know in discussing what if's...like I said earlier, I think we made out pretty good in the trade all things considered.
I'd say it was a win/win for both teams. Even more so for us in the long term since we don't have to be responsible for his next contract.