In the years where the Line backing was a team strength, they seldom had more than three genuine players at ILB and OLB. The balance of the LB squad were Larry Izzo, ST types.
Yet that was called good depth. More often than not, one of the big six was injured. One year it was TJ; another year it was Tedy; another year it was Colvin. Willie would periodically have problems with his recurring back injury, etc.
Numbers wise we have more genuine LBs today, rather than pure ST types. The question is whether we have enough "good" ones. From my perspective, Pierre Woods won a job as a regular last year, only to see it ended by an IR Jaw injury, three games later. I thought it was very significant hat he forced Vrabel to the weak side; and even more significant that Belichick freely traded Mike in the Offseason.
Crabel was a scrawny, but prized high draft pick, that everyone said needed a year in the weight room. He has had that now. TBC is a proven better than average pass rusher, and NFL level reserve, at WOLB. So he fits as an Adalius backup.
Whether the Patriots can find one starting quality player out of those three, Woods, TBC, and Crabel, with a possible but unlikely addition of Redd, we fans just don't know. But the Coaches seem unconcerned, and they see these guys close up, unlike us.