Justin Fields did not throw the ball very often in his first two games. However, we did see enough from Fields against the Green Bay Packers that there are definitely things to clean up. The Chicago Bears quarterback is still young and now is in a new offense. On the road for a primetime game against a division rival was going to be tough for him.
Still, the following plays are things that cannot happen, and we must see the progression.
3. Missing open wide receivers
The play linked here has been circling around the internet. Equanimeous St. Brown is wide open streaking down the field for a third down touchdown, but Justin Fields decided to check the football down.
Below is another example of a missed play. Below you can see in the still image that as Justin Fields gets to the back of his drop he is reading the right side of the field.
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You can see that the Bears near the right hash are breaking near one Packers linebacker. The LB is in a tough spot and in the next image you can see that he is trailing. However, at the same time, now that he has his back turned to the quarterback, it also opens up the check-down to David Montgomery.
Justin Fields is reading this side of the field and should see that two players are going to break open running out towards the sidelines.
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Unfortunately, you can see the play below. He starts to get pressure from the right tackle and it takes is mind off of reading the field. So, he starts to get happy in the pocket, and eventually runs into a sack from the pressure on the other edge.
This is a pass that Justin Fields has to complete. Whether he checks it down, or they take advantage of the linebacker who got turned around, the play call was designed for him to read that side of the field, he did, and he still did not pull the trigger.

2. Chicago Bears issues taking the snap
Early into the game, the Chicago Bears had an issue with the snap. It is tough to tell for sure, but it looks like the issue may have been on Sam Mustipher. Either way, the two not being on the same page cost them a play.
Below, we see another issue between Fields and Mustipher. You can see that Cody Whitehair taps Sam Mustipher, usually a sign to snap the football on the beat called out in the huddle.
However, in the play above you can see that this does not happen. Mustipher starts to tap his leg, and Whitehair looks back at Fields like he does not know what Fields is doing.
The three are not on the same page, and it results in a bad snap and one that Fields is not ready for.
Fields tried to save the play, but two times the team lost plays because of snapping issues. The first one looks to be on Mustipher, but this one looks like a clear communication breakdown. This is on the quarterback to have the lineman on the right snap cadence so that they are not shrugging their shoulders seconds before the snap.

1. Throwing the ball past the line of scrimmage
Of all of the mistakes that Fields made against the Packers, this one is probably the worst. It speaks to the idea that things are moving too fast for Justin Fields. Fields escaped the pocket on a third down pass and went into scramble mode.
However, after running about five yards downfield he saw a wide receiver open and decided to throw it. Of course, that is illegal.
This is an issue because Fields has to have a better understanding of where he is. This goes back to the play where pressure caused him to take his eyes off of the field and then scramble into a sack, rather than making an easy completion with players swarming him.
The same thing happens here where Fields is clearly not sure in himself and is not even sure where he is on the field. He is improvising based on the last split second, while quarterbacks always need to be two steps ahead.
The good news is that things can continue to slow down for Fields. However, we have to see him more composed when pressure comes. He has to be able to stand in the pocket, keep his eyes downfield, and make throws without worrying about who is coming and from where. Too often, that is holding him back.

