If we look at objective measures designed to get to the heart of what a quarterback is contributing to a team, Case Keenum is playing at a higher level so far in 2017 than any Vikings quarterback has played over a full season since Brett Favre in 2009.
Yes, Keenum has been better than Sam Bradford was for the duration of 2016. Yes, he's been better than Teddy Bridgewater was in 2015 or 2014. He's certainly delivered better than any QB play the Vikings received from 2010 through 2013.
Before you dismiss this as nothing but a ridiculous hot take, let me explain:
There are no perfect metrics when evaluating the play of a quarterback in a vacuum, but three that aim to do a pretty good job are Total QBR (developed by ESPN) as well as defense-adjusted yards above replacement (DYAR) and defense-adjusted value over average (DVOA), both used by Football Outsiders.
Total QBR, developed in 2011, "incorporates all of a quarterback's contributions to winning, including how he impacts the game on passes, rushes, turnovers and penalties" while also seeking to contextualize success or failure depending on game situations. DYAR and DVOA attempt to do similar things, with different formulas.
Keenum so far this season ranks No. 6 in Total QBR among NFL QBs. He's No. 5 in DYAR and No. 4 in DVOA. There are only three QBs in the NFL who are in the top six in all three categories: Tom Brady, DeShaun Watson and Keenum.
Bradford in 2016 — despite the consensus being that he played well and despite him setting an NFL record for completion percentage — finished No. 17 in ESPN's Total QBR standings, No. 16 in DYAR and No. 17 in DVOA. That's decidedly average.
Bridgewater in 2015 finished No. 17 in Total QBR, No. 21 in DYAR and No. 22 in DVOA among NFL quarterbacks. Bridgewater ranked even lower in all three categories as a rookie in 2014.