There's no way of knowing whether or not McDermott's poor game management in the 4th quarter was a contributing cause to the loss. It certainly could have been (I think it was) but we won't know because we don't get to see the parallel universe where McDermott's game management wasn't inexcusably awful. Unfortunately.
But that doesn't mean we can't point out how horrible it was. And how much of a concern that is with regard to the future of this franchise.