A few weeks ago, the clear-cut starting quarterback for Tennessee was Ryan Tannehill. For Atlanta, it was Desmond Ridder. When the Titans and Falcons next take the field, neither might receive the opening snaps. Triggering a switch would not be injury — the usual cause — but performance.

In the Titans' case, it would be a splendid performance. Will Levis, who had yet to play before facing the Falcons, became the third rookie QB to tally four touchdown passes in his NFL debut. (The others are the legendary Fran Tarkenton and the not-so-legendary Marcus Mariota, who did so as a Titan and preceded Ridder as the Falcons' starter.)

In Atlanta's case, it would be an awful performance. Two, actually. Ridder was removed at halftime after surrendering his fourth fumble in two games and taking five sacks. He was checked for a concussion Sunday and cleared. Veteran Taylor Heinicke entered for his initial appearance this season and generated 20 second-half points to rally the Falcons to an ultimate five-point defeat.

A few weeks ago, the chances were remote that Levis and Heinicke would earn promotions by the first Sunday in November. Now, it could happen. Such is the transitory life of an NFL quarterback, and our rankings are shaken up a bit as a result.

Of course, injuries remain impactful on swinging the revolving QB door. Minnesota's Kirk Cousins is done for the season with an Achilles tear suffered Sunday. Pittsburgh's Kenny Pickett and the Giants' Tyrod Taylor, himself filling in for Daniel Jones, bowed out before halftime with damaged ribs. The Rams' Matthew Stafford was sidelined with an ailing thumb.

For each player on our list, we provide his MVP odds if applicable, a QB2 rating that indicates how much a team's power rating is downgraded if the starter is out and projected fantasy points per game.

Which QB offers the best value in the MVP race? And which signal-callers are on the rise? ... Join SportsLine right now to see Week 9 QB Power Rankings from veteran writer Mike Tierney, including how to bet when injuries strike and SportsLine projections for all 32 starters!