It will be an issue. Fields will struggle in an offense that plays into his weaknesses (quick game) by necessity. WRs aren't good enough to get open quickly and aren't big/strong to escape jams. The contracted offense limits YAC potential of the fast guys.
Teams blitz the hell out of the B and C gap to blow up the outside zone game in the backfield. The limited O line experience on the outside negatively impacts cohesion and blitz pickup.
Fields has a number of big runs due to the defense getting upfield too quickly, however because he doesn't have the option of long developing plays, he starts to drop his eyes and look to run too quickly. This causes him to get hit and injured. He's tough, so he plays with it, but it limits his effectiveness.
In spite of that, Fields flashes still because he is the man, but everyone starts to turn on him anyways. Bears finish #26 in total offense. #29 in passing.
The Bears load up on O line and weapons next year, and hopefully Fields hasn't been David Carr'd by that point.
Feel free to save this because if I'm eating crow here, I would be happy as hell.