IMHO, decision-making is the most important element of success for a QB in the NFL, followed by accuracy, toughness (mental and physical), arm talent, and mobility, in that order. After this many years watching Brady, this is what has become most clear for me.
Thus in assessing Darnold, who I liked watching in college, my biggest question is about his decision-making and accuracy. His biggest issue last year in college was turning over the ball, both on INTs and fumbles, and the Pac 12 wasn’t all that strong as a conference last year. Now he is starting Game 1 with all the pressure that entails for even experienced QBs while simultaneously trying to correct his biggest flaw from last year. I think it’s a very tall order for him and was pretty surprised that Bowles didn’t wait until Darnold had a decent number of snaps through say 4 games backing up McCown (similar to how Parcells eased in Bledsoe behind Secules in Drew’s first year).