Spikes brings the FIRE and intensity that this defense just didn't have last season. Just watch him, he may not run a fast 40, but he is a big mean, instinctive, football player. Those bone rattling hits over the middle, definitely pump up the team and the crowd.
Mayo is more of a lead by example, blue collar type guy. Spikes looks like the type who can light a fire. And that's a huge part of football as well. Leadership is often underrated until its gone. When we lost guys like rodney, bru, mcginest, etc. This defense was suddenly just not the same again.
Spikes is one of those players that most everybody recognized was good and fit the Pats style of defense, but we 'talked ourselves' out of it. His 40 time is too slow. He's not as good as McClain (but who is??), etc., etc.
BB looked at the film, evaluated Spikes, and may have come up with a special player. I mean just look at the effect that KG's intensity has had on the Celtics. If Spikes can bring that kind of intensity and plays well in the SILB role to boot, the Pats defense could show some real improvement!