Isaiah Frey is going to be the de facto winner of the nickel back competition with Zackary Bowman, and it's not through Bowman playing badly at all - rather, the rough circumstances of Bowman leaving Friday's game with an injury. That being said, Frey was on the way to winning that competition and only further solidified his case with an interception on Friday night. It wasn't a good throw by Matt Flynn, but it was good recognition by Frey and a great play on the ball.
The defensive line is probably the strongest unit on the roster, and that's exactly what you want with Julius Peppers, Corey Wootton, and last year's first round pick Shea McClellin growing into the position a little more. But Stephen Paea had probably the best game on that unit (which, facing a bad offensive line like the Raiders, means something when looking at the rest of the Bears' linemen). I thought he displayed some strong consistent penetration.
But two guys that showed up yesterday were Christian Tupou and Cornelius Washington, and Washington is playing like he demands a spot on the team despite lining up against the twos and threes. Zach Minter moved into the defensive tackle spot first, but didn't do much to help his case, and Tupou had a couple of impact penetrations despite Sam Rosen not being able to read his name through the hair. Not sure Tupou's got a spot on the team, but I don't think I can argue much against bringing Washington to the 53-man as the fourth or fifth end and letting him hunt quarterbacks on third down (I don't get the impression Kyle Moore's staying). If he gets cut, I don't think he makes it to the practice squad without getting claimed.
I'm not overly worried about Jonathan Bostic, but I do have a series of concerns. I think eventually he'll learn coverage, but right now, he has to be the guy coming out in nickel situations, which is odd considering for ten years it was the strong-side LB coming off, always. Or that's just because Brian Urlacher and Lance Briggs were nuts on the field. Just a hunch.
But that being said, I don't think the Bears can afford to not let Bostic play in normal 3-LB situations. He needs reps, and I think he'll get them. And there's enough talent elsewhere on the roster that the defense can ride out the mistakes of the linebacker in the middle, especially if the defensive line picks up the slack like they should have the talent to.