Let's say there's a 10% chance that Sloter could turn into a starting QB, maybe like Kurt Warner as some have suggested, to take over after Cousins...AND there is a 10% chance that Mannion helps Cousins play better for the Vikings, as NFLDraftGuru has suggested. Which would you give more playing time?
I would favor Sloter, because I'm a fan of the team and will be for the rest of my life, hopefully after however long Kirk Cousins stays, and a lot of people on this board probably would as well.
But will Rick Spielman be a lifelong Vikings fan - if, say, two years from now he is the Assistant Director of Player Personnel for the Chargers?? No, so how would he answer that question?
Hey, Spielman is not a terrible GM and he isn't the antichrist. He has brought good talent and coaching here...BUT...he hasn't been able to find a winning QB. He's got big "F" grades for Ponder and Bradford, and the Wilfs probably give him an "Incomplete" for Bridgewater (though neither his 14-TD season or anything he has done since leaving Minnesota suggest that Spielman had found a HOFer and lost him to injury). Then there's TJack and McNabb, and Spielman might say they were picked by then-coaches Childress and Frazier - but he takes credit for drafting Adrian Peterson while Childress was coach, so...no blame taken?
Point is, the Wilfs seem to like Spielman and Zimmer but they have to have a GM and coach who can pick/develop a QB or the team is incomplete. At QB selection, Spielman is at best 0-2 with 3 "not my fault" failures. They let him drop a 13-win QB to sign Cousins to a rich guaranteed contract. Do you think they keep him around if Cousins is so bad he needs to be replaced by Sloter a year from now or sooner? And do you think Zimmer wants to bet on being retained by Spielman's replacement?
So if you're Spielman and Zimmer and your job and career are 100% dependent on Kirk Cousins getting the Vikings to a Super Bowl in the next two years, and you have the same options - Mannion having a 10% chance of improving Cousins vs. Sloter having a 10% chance of being a starting QB for whoever takes your job - how would you answer? Mannion, even if his odds are lower and Sloter's are higher.