I got in a lot of arguments on here back when this happened. Practically speaking, in his first 3 drives, Jalen was just about as bad if not worse when considering the fumble.
There's only a little from before he was pulled out of the game (and most of my worries with him were written on his face and not on the field). He didn't look that bad but you can kinda briefly see how jittery he looked. Would he have settled down? Possibly. But Jalen didn't give him that opportunity. When he came back in with no pressure he did a lot better.
I'm fine that we let Jalen continue to start but Blake had 3 drives and Jalen had 3 drives and they were both miserable. Honestly neither were impressive and both looked out of sorts. Jalen's face didn't show emotion but he played tight. I think Blake is the real deal and can be a heck of a QB. He probably shouldn't have said anything about it at all but many on here did seem to think he was rattled and timid, which he likely was - but Saban said after the fact that the plan was to put Jalen in after 3 drives anyways.