I talked a lot about this after the draft so much that it made me seem like a hater (which I'm not).
His arm motion is similar to Carson Wentz. When he really rips it, in his setup his hand is below his elbow. That motion takes a bit longer to release, but it also puts the ball in a risky spot because pass rushers can swipe at the ball causing a fumble.
What makes this motion worse for Fields is that he has relatively small hands. They are 9 1/8 inches, which is on the small side.
What further compounds this is Fields style. He's not like Drew Brees or Tom Brady where they get the ball out very quickly. He uses his athletic ability to buy time.
Each one of these items individually aren't too bad, but the combination of things could be costly.
Buying time + longer arm motion + smaller hands = turnovers.
Personally I see a lot of Carson Wentz in Justin Fields. That comment goes both ways. Not too long ago Wentz was playing MVP caliber ball, so try not to read that as strictly negative. BOth look to extend plays, have longer throwing motions and have a bit of a turnover issue. With that being said, the largest current problem with Wentz is that he's not that coachable and wanting to do things 'his way'. I don't see that in Fields, so if you get all the positives of Wentz and the ability to remove the bad, there's an amazing QB.