... Remember Mariota and Monday nights game against the Texans.
Mariota went 22-23 with a perfect passer rating. And yet the Titans were not competitive. This tweet does a good job of explaining why his stats did not match the eye test.
This reminds me of Dak against the Commanders. He was awful essentially the entire game. And yet due to two passes his passer rating was stellar. Eye test > Stats in this case.
As a reminder Dak is 23rd in the NFL in QBR. Top 5? Brees, Mahomes, Rivers, Goff and Wilson in that order.
For added Dak context Joe Flacco and Ryan Fitzpatrick have been better. Fitzpatrick has been benched twice and there is talk Joe has been Wally Pipped. Meanwhile we wouldn't trade Dak for 2 first rounders and are backing up the Brinks truck. Future is bright!
You are making an argument based on 1 game for Mariota.
You might be correct, but your post does not prove anything either way.
A good study would be to look at the QBR for the past 10 years of Quarterbacks that made it to the Super Bowl (both winners and losers of the Super Bowl).
Look at their QBR for that season, that post season and the Super Bowl. Also look at their career QBR and the average NFL QBR of teams with winning records vs losing records in those time frames.
Then look at the QBR allowed by the defenses on those 20 QBs teams (regular season, post season, Super Bowl) as compared to the average in the same time frames to see how much those QBs defenses helped them.
If your goal is to show that QBR is better than QB rating, then show the rating as well.