Marc Trestman’s first season with the Bears was about reinventing the offense, and it’s hard to deny the success he had along the way. I’m now wondering if Trestman’s second season at the helm will be about reinventing the Bears defense.

While it’s entirely possible that I’m reading the tea leaves and getting the answer that I want to see, Thursday brought yet another sign that the Bears are considering switching to a 3-4 defense.

The Bears officially announced the hirings of Paul Pasqualoni and Reggie Herring on Thursday. Pasqualoni will coach the defensive line, and Herring will coach the linebackers, replacing Mike Phair and Tim Tibesar respectively. Well, following a season in which the Bears defense was absolutely dreadful, they decided to fire their defensive line and linebackers coaches. Mel Tucker, the man in charge of the entire defense, was retained.

Now why would you fire your position coaches on the defensive line and linebackers? It’s almost as if you’re planning some kind of major change to those two positions when you do so. Like, say, I don’t know, reducing the number of defensive linemen you use to three and adding a fourth linebacker.

Then you hire guys like Pasqualoni and Herring. Now, Pasqualoni has coached a number of different defenses during his long career. He can’t be pegged as a 4-3 or a 3-4 coach. He’s done both. But Herring’s situation is slightly different.

Herring coached the linebackers with the Cowboys from 2008-10 and with the Texans from 2011-13. The head coach while Herring was in Dallas, and the defensive coordinator while he was in Houston was Wade Phillips. There’s no question as to which defense Wade Phillips has preferred throughout his career, as he’s run the 3-4 everywhere he’s been.

Now it’s possible that the Herring hire is a red herring — sorry but I had to — but I don’t think that’s the case. I don’t know why the Bears would hire a linebackers coach with so much experience coaching in a 3-4 system if they weren’t planning on making the transition themselves.

Particularly when you hear Phil Emery say things about needing to find a place for players like Shea McClellin — who is a bad DE in a 4-3 but could be a useful rush linebacker in a 3-4 — and also mentioned the possibility of moving Jon Bostic from a middle linebacker to an outside linebacker position.

So you’ll have to excuse me for being a bit giddy about all this, because I think it’s finally happening.

Now, on the surface the difference between a 4-3 scheme and a 3-4 scheme might not seem like much to you. You simply replace a defensive tackle with another middle linebacker. Well, it’s not that simple. The kind of personnel you need at each position in a 4-3 and a 3-4 are entirely different. For instance, instead of a Tommie Harris kind of defensive tackle we’ve seen here for years in Lovie Smith’s defense, we’d now be looking for a Vince Wilfork. A large man to plug space. Also, the defensive ends aren’t the same kind of pass-rushers in a 3-4 that they are in a 4-3, and they’re generally bigger.

Those are a few basic differences, but the reason I prefer the 3-4 is simply the philosophy of the defense. It’s much more aggressive, and I always prefer to be the aggressor. While the Tampa Two — which really wasn’t a Cover-2 at the end under Lovie, as the Bears ran more Cover-3 and Cover-1 than Cover-2 the last few years as Urlacher aged, but I’m not going to get into all that — was effective for the Bears, it was a defense more about sitting back and waiting for the offense to make a mistake, and then capitalizing on that mistake.

The 3-4 is trying to force you to make that mistake. There’s generally more blitzing in a 3-4 because you have “more” options in doing so, but it’s not just that kind of aggression. As the NFL changes and becomes more of a passing league, I’d rather have four linebackers on the field than defensive lineman. Linebackers that can cover the kind of tight ends we see exploiting the seams of the field these days. Between the pressure aspect and the athletic aspect, I just believe the 3-4 to be the more capable defense these days, which is why we’re seeing such a shift toward it throughout the league.

The Bears were behind the curve on modernizing their offense, but they caught up. Now it’s starting to look like they want to catch up on defense as well.

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