i see no reason for utah to accept this.

Just nonsensical. Utah giving up so much for one year of Marner or Marner even waiving.,

why would the coyotes/ARZ/UTAH do this?

The difference between Keller and Marner is not huge, and probably favours Toronto based on contract alone (Keller is almost a ppg at 7.2mil signed for another 3-4 yrs, Marner is over a ppg but an 11mil UFA).

But they add a rookie dman who just got 26 pts in 80 games?

Your probably right, might be more of a scenario if Keller wants out. But yes very unlikely

even so - keller has four years left at a good number. marner has one year left at a bad number and then is UFA. If I'm running Utah, and Keller asks out, there is no way i'm taking this deal.

you could tell it was going to be delusional because they are still in the "if" stage.