saying he sucks in the clutch is different than saying he's not realizing his potential (like you said in your earlier post).
Those are two different assertions.
Also, just for the record
Kyler Murray has 11 career fourth-quarter comebacks and 13 game-winning drives, according to Pro-Football-Reference.com. These stats reflect his ability to lead the team in crucial moments during games.
So it's not like he's not capable of being good in the clutch.
Just something about important games seems to affect him negatively.