We're talking 60-70 yards in the air back the opposite direction from his scramble and on the wrong side of the body for a right handed QB.
You're talking a super human throw as otherwise Evan had plenty of time to get to any sort of realistic pass that his man could have gotten to.
Now, I won't ever argue that it's ever smart to leave your man while the play is still live with the ball in the QB's hands, but he was not in any real danger at that point. That is who Jennings was likely trying to heave the ball to, and look where the ball landed. It never had a chance.