I think this is a serious question in theory, and ought to be one in practice, but I would be shocked if Gary Kubiak will give it any consideration.
Anyone who saw yesterday’s game can appreciate, in every sense of the word, that at this point Manning is being held together by whatever the high-tech medical equivalent of duct tape might be. Sometimes his passes look like the work of the old (meaning the younger) Peyton Manning; more often they can look like a pale imitation of the former; and sometimes they resemble the proverbial duck that has come within range of a well-armed blind.
Manning had several throws yesterday that almost tumbled over end-to-end. The one time he threw deep he missed an open Demaryius Thomas badly. He lobbed a softball over the middle on an intermediate crossing route that William Gay jumped so easily that he quite possibly would have it returned for a pick-six, save for Emmanuel Sanders doing his best Charles Woodson imitation and breaking the play up.
Manning has also lost what mobility he once had, and he makes an extremely tempting target for pass rushers. The Broncos longest play of the day came when he fell on his face while dodging one, and then jumped up and found an open receiver when the Pittsburgh defense seemed to assume for a moment that the play was over.
The Broncos’ offense sputtered mightily against a dubious Steelers’ defense, effectively generating just 13 points, even though Denver had great field position all day. (Three “drives” started deep in Pittsburgh territory, and yielded nine points, no thanks to the offense, which made one collective first down on those three positions).
On the other hand:
(1) The Bronco receivers had a half-dozen flat-out drops. Manning didn’t look good by any means, but his teammates made him look worse than he actually was.
(2) While saying that Brock Osweiler is at this point a physically superior quarterback to Manning is like saying that Barack Obama is better at electoral politics than Jeb Bush, it’s far from clear that the right call is to yank Manning for a guy who, although he has played fairly well in his grand total of six career starts, is a guy with six career starts heading into the AFC championship game.
If you could graft Manning’s head onto Osweiler’s body you would have a superstar quarterback. That option isn’t available. So do you go with an all-time great who may or may not have a bullet or two left in the chamber? (Manning took a couple of ferocious hits yesterday, after missing almost all of the previous two months of action, so who knows what sort of shape he’s in now). Or do you roll the dice with the promising kid who has never been in anything like this situation before?
I think it ought to be a really tough call, but unless you’re a Bill Belichick type, which is to say a coach with a genuine DGAF attitude, you’re going to go with what feels like the safer option, and that’s Manning. Of course if the Broncos’ offense looks as bad against NE as it did yesterday they’ll probably be down 13-3 or something at halftime, and then Kubiak may re-evaluate.