And the reason is simple: Bunkley better fits the new scheme.
New defensive coordinator Juan Castillo has already made it very clear that defensive line coach Jim Washburn will be able to do whatever he wants with the guys up front. It will be Washburn's scheme, and Castillo, along with Mike Caldwell, Mike Zordich, and Johnnie Lynn will have to work accordingly.
In Washburn's scheme, the defensive ends go after the quarterback. That's been talked about to death, so we all know that, but something that's not being talked about is the fact that his defensive tackles also play a one-gap responsibility rather than two.
Under Sean McDermott (and, to a degree, Jim Johnson as well), the defensive ends were taught to look inside and play run before attacking the quarterback. That half-second on every snap was the difference between a sack or a touchdown pass on several occasions.
McDermott (and, again, Johnson) also had the defensive tackles responsible for two gaps on every snap. Since they usually would line up either in, or close to, the B-gap, they would have to sit in the B-gap and squeeze the A-gap. That meant taking on the guards and driving them inside to create a pile in the middle.
That, of course, is the job description of a big defensive tackle weighing somewhere between 320-340 pounds -- not for someone the size of Bunkley who is generously listed at 305 pounds.
But Bunkley did it, and did it well for a couple seasons. However, he struggled in 2010 and then injured his elbow. If it was going to be tough for him to play a two-gap system before, it was going to get even tougher with an elbow injury that was obviously going to hamper his upper-body strength.
Enter the 330-pound Antonio Dixon who fit the scheme perfectly, and we have what appears to be Dixon drastically out-playing Bunkley.
That, however, was not necessarily the case.
Bunkley is still the superior player. In a one-gap scheme he could easily be one of the most disruptive defensive tackles in the entire league. He has a very good first step off the ball and if he's allowed to use that speed through the gap rather than sitting and trying to create a stalemate at the line, we could see a very different Bunkley than we've seen recently.
In fact, we could even see the pass-rusher the Eagles thought they were getting back in the first round of the 2006 draft.
This is not to say that Dixon will be useless in this new scheme; he's a very good player who, after shedding a few pounds, can still be very productive in this new system.
However, it would not surprise me in the least to see him go from a starter to the fourth guy in the rotation underneath starters Bunkley and Patterson, and former second-round pick Trevor Laws who, like Bunkley, should thrive under Washburn.