Craig Robertson

You are failing to account for the fact that Robertson tends to play 16 games a year and Anzalone tends to play 4-6. Therefore, Robertson's experience is growing at a higher rate and Anzalone's is stunted. Robertson is aging, but Anzalone is not getting any younger and injuries take a toll beyond their years. Robertson is overall more likely to improve than Anzalone, because Robertson can stay on the field to improve his craft. You are basically projecting how great Greg Oden would be at 30, Anzalone will likely be retired before Robertson.

I don't think Robertson was better than Anzalone, but if he was, the difference was insignificant. I saw Anzalone making very good plays in his 3.5 games last year, and that was as a rookie. I think the difference is that if Anzalone can play at a comparable or near comparable level now, then it is expected that he will be able to play at a much higher level after he gets more experience. Robertson is a very solid LB, but Anzalone is good now, and potentially great.