As a Fleck defender, maybe I haven't expressed it, yes there are concerns.
Here are the concerns I have:
1. Overall Defense. I'm not sold on Robb Smith and haven't been. I don't know how much is REALLY on him vs personnel. My guess is both. Seems like some teams can coach defenses where the players are more interchangeable, where we turn to absolute crap the minute our one player goes done. Granted, there have been more injuries since then, but schematically we must have razor thin margins for errors which we didn't have with Kill / Claeys.
2. Defensive line. We have guys playing out of position and next year will likely be worse. Fleck has a good class of D-lineman coming in, but I assume they will all redshirt next year so our defense will be younger.
3. QB. I'm not sure either QB is Big Ten title winning caliber, but both are serviceable and we use a third option with Wild Cat to help change things up to compensate. Also, I think we have better QB's coming in recruiting. These should arguably be the worst two QB's Fleck has during his tenure here.
4. O-line. This was a concern until two weeks ago. Now it looks like our second best area of optimism after our WR's.
5. RB's. - I don't think our freshman are great. I think SB4 and RS1 are both head and shoulders better RB's than what we've recruited with Fleck so far. This needs to improve.
I'm not concerned with Fleck from a recruiting standpoint. He's delivering there.
I'm not concerned with Fleck from a coaching standpoint. He seems to make decent judgements with his game day decisions (but this can be nitpicked apart 6 times a game).
I'm not concerned with what he's saying. He's largely telling the truth from what I can tell with the regular coach spin to protect his players as much as you can while still explaining why the defense allowed a 65 yard run.
The biggest concern I'll have with Fleck is if he is staying loyal to a bad Defensive Coordinator too long out of loyalty instead of cutting bait at the point Fleck believes there is a real issue. My guess is Fleck is talking to people in his network about how to know when it's the right time to pull a plug on a guy, but at this point, I think he believes in the scheme and that with the right players, it will work. If that's the case though, PJ has to know what his timeline is for this improvement because the wick is already lit on the bomb so he has to know if he needs to cut it or not.