He was 80 for 84 on passes behind the LOS in 2016. Take away those throws and his throw aways, and he is a 49% passer.
He is a 42% passer on throws 10+ yards beyond the LOS.
He is a 33% passer on throws 20+ yards beyond the LOS.
And he is a 30% passer when under pressure.
Considering the caliber of OL he plays behind, the quality of WRs he is throwing to, and the effectiveness of play action due to his running game, these number are pretty atrocious. To even suggest that Tanner Mangum wouldn't be much more effective is just being stubborn.
https://www.seccountry.com/alabama/look-jalen-hurts-passing-chart-reveals-trends-will-make-alabama-fans-uneasy