Bill Belichick was a guest on Sirius XM NFL Radio's "Movin' The Chains" program today, and he was dishing out some top-notch insight to hosts Pat Kirwan and Tim Ryan. It's clear how much respect Belichick has for the co-hosts based on the quality of answers he provides.

The biggest thing learned from this perspective was why Belichick switched to a 4-3 defense this year.

This was a topic Belichick had been reluctant to address in training camp, deflecting talk of differences between the 4-3 and 3-4. But five games into the regular season, he was more willing to delve into the topic with Kirwan and Ryan.

"We've played a mixture of odd fronts and even fronts, but I just felt like from a starting point -- given the lack of spring opportunities to practice and meet, and the shortened training camp in terms of actual number of practices -- that from a teaching standpoint we felt like there would be more carryover teaching our base defense and nickel defense really as one front," Belichick explained (short audio clip here).

"We wanted a lot of carryover between our run responsibilities and run fits, and some of our pressure defenses and things like that. We'll transition and build into some of our odds fronts, but we felt like in trying to evaluate young players, asking them to learn one system in a 3-4 and then learn another system in nickel [was too much]. As you know, we were in nickel defense just as much as we were 3-4 defense because of teams using multiple receivers on early downs and two-minute and all those kind of things.

"So we felt like it would be a better opportunity to evaluate our players and not try to over-install and put in a ton of defense. Try to cut it down a little bit and see if we could execute it better. Certainly, we have a long way to go but I do feel like we're making progress, and I think our players at least understand what we're doing.

"There are so many intricacies to a 3-4 defense that I just didn't know if we'd be ready to handle them this year. Probably wouldn't have been, to be honest with you."

A few other nuggets from Belichick:

On Ryan Mallett: "Ryan's doing well. It's certainly great for him to see our other two quarterbacks, Tom and Brian Hoyer, to prepare on a daily basis. Of course, he's had an opportunity to go out there and run scout-team plays, up against our first defense. ... He's had a good opportunity to learn and improve, and do things off the field that can help him get better. And he's worked real hard at that. I think he's making a lot of progress."

On Andre Carter: "He's doing great. He's so professional, a great example for all of us -- younger players, older players. He comes early, stays late, works hard, is in terrific condition, can run all day. Really takes his job seriously, wants to do everything right, very team-oriented. He's been a pleasure to coach. He was a guy we looked at pretty closely when he came out of Cal. It was 10 years ago when the 3-4 was really our base defense, it was hard to find the right role, the right impact for him, in that. I personally went out there and spent a lot of time with him, and loved everything about him, except the fit he would have in a 3-4. Fast-forward a decade later and we made that decision to kind of transition our front a little bit this year, and he was really the perfect guy for it. I do think from a skill-set, that's what he does best, and that's what we're asking him to do. It was a great fit and we get all the character and leadership and work ethic of his game along with it. So it was great."

On Shaun Ellis: "Shaun played most of his career on the left side, and Andre has played most of his career on the right, so it was really a good match for us to have those two veteran players with not only the quality of play, but the type of individuals they are -- the leadership, the toughness and the work ethic and dependability and professionalism that they come in with every day. It's been great, along with some of our other players, like Vince Wilfork, Mayo, Rob Ninkovich, and younger guys like McCourty and Chung, guys like that. Really, from a team chemistry and communication and working standpoint, it's been very good. Shaun has added a lot to our team, and so has Andre."