"...when he's not playing well the Bears would be better off having pretty much any randomly selected member of the team lining up under center." Don't be silly. I have seen pretty much that in the past. It is far uglier than anything Rex has done.
Even after posting horrible numbers in two of those games Rex brought the team back to win and in another it almost pulled out a victory. Grossman has shown the ability to come back from a decifit and a bad showing.
He has great potential and should be our leader for years to come. If allowed to become a free agent after this year Grossman will get huge offers from other teams.
you can't get uglier than a 0.0 QB rating.
Rex had nothing to do with the comeback against AZ, the best he managed to pull in that game was to stop screwing up and actually give the defense and special teams a chance to pull off the win. Same thing in Minnesota. The only reason they even came close in the NE game is that Brady was having almost as bad a day as Rex. So no Rex hasn't shown that at all.
Many players have great potential, but Rex also has shown the potential to be a terrible game losing QB. I doubt Rex will get huge offers, any GM willing to fork over a huge contract to a player who had games like that, especially one carrying Rex's injury baggage, should be fired on the spot. If Rex hits free agency he shouldn't be given any offer bigger than any other normal so-so journeyman, maybe strap some incentives onto it so that if Rex actually does improve he can turn the contract into something big. But there's just no way a guy finishing his only year as a fulltime starter with 20 INTs and 8 fumbles should be handed star QB money.