The change, when measured in cold, hard numbers, is startling: Jim Johnson's excellent defense allowed an average of 120.1 rushing yards per game from 1999-2006, ranking 24th in the NFL. In 2007-2008, the defense ranks fourth in the league in run defense, allowing an average of 87.9 yards per game.

What a difference. Why? How? Could it be just the combination of Mike Patterson and Brodrick Bunkley at defensive tackle? Is it more of a commitment to stopping the run? Is it the linebackers, all of whom are in their third season or less in the bigs?

What is the reason the Eagles, who rank first in the NFL allowing just a shade over 45 rushing yards per game through three games, are so stingy against the run?

"It's a lot of things," says defensive coordinator Jim Johnson, "but you can start with the tackles. Mike and Bunk are playing great football. I said this before: I don't think you're going to find tackles in this league who are better against the run. They work hard, they play with discipline and they play off of each other. There are a lot of other players involved, of course, but those two are really getting after it."

The 87.9 yards-per-game average since 2007 (opponents are averaging 3.6 yards per carry against the Eagles in that time) ranks fourth in the NFL, behind Minnesota (73.5 yards), Baltimore (78.4 yards) and Pittsburgh (85.8 yards). It is an impressive statistic for a lot of reasons, one of which is the idea that a "smaller-sized" defensive line can't do the job against the gigantic lines around the league these days.

"We have good guys on this defense -- ends who hold down the edge, linebackers who are big guys, young guys who run around and get to the ball -- so it isn't just the tackles," said Patterson, in his fourth season with the Eagles. "I love working with Brodrick. I think we work well together. We complement each other's games. He's a good player. He is an explosive guy who helps me.

"As for the size, it matters how you play. If you try to go 'man up' all the time, you're going to have some things going on that may not work in your favor. We don't do that. It isn't all about the strength all the time. We use our speed and quickness and we get to the ball."

No doubt they are doing that. St. Louis had 15 carries for 36 yards in Week 1. Dallas, with its dangerous duo of Marion Barber and Felix Jones, gained 68 yards on 24 carries. And Pittsburgh, traditionally one of the most powerful and physical running games, put up 33 yards on 19 carries, an average of 1.7 yards per rushing attempt.

It is a dramatic difference from earlier versions of Johnson's defense. It isn't fair to say that Johnson was OK with allowing a big run here or there, but it didn't bother him as he answered questions during his weekly press conferences that the run defense was being probed. Was it good enough? Johnson always said he would get the run defense where he wanted it to be by the end of the season.

But in the playoff loss at New Orleans that ended the 2006 season, the run defense had major problems. The Saints rolled up 208 yards on 27 attempts.

Johnson knew he had to do something.

In the period of time since then, the front seven has been overhauled. Only Patterson and Trent Cole remain starters from that 2006 playoff game, although to be accurate Omar Gaither was the WILL linebacker in that game, too (He doesn't count here because he moved to the MIKE position last year and has since moved back to WILL).

Anyway, the Eagles made some dramatic changes. The traded Darwin Walker once they determined that Bunkley, coming off a very difficult and unproductive rookie season, was ready to start at tackle. They went young at linebacker with Stewart Bradley and Chris Gocong, flushing out veteran Takeo Spikes after a one-year trial period.

The draft brought in reserve tackle Trevor Laws, free agency netted reserve tackle Dan Klecko and end Chris Clemons and Darren Howard became a rejuvenated player for 2008.

If you believe that results speak for themselves, the Eagles are where they want to be against the run.

"It's a long season and we are off to the kind of start we want," said Patterson. "You really have to take care of the run. You know that every team is going to try to establish the run against you, so you have that challenge every week. If you play well against the run, everything else is a lot easier.

"We're playing on the same level and on the same page as a defense. I think we're only going to get better."

The next foe is Chicago, which pounds it with rookie Matt Forte on the ground. The Bears could surprise and come out throwing the football all over Soldier Field, but common sense says Chicago is going to try to get the ground game going and look for some big plays off the play-action passing game later in the contest.

"I don't doubt that they are going to try to run the ball early," said Patterson. "Most teams do. We have to play well against the Bears. They're a very good team."

Bunkley seems to have taken the next step in his development, which is huge for a team that used back-to-back first-round draft picks on defensive tackles (Patterson, 2005 and Bunkley, 2006). Bunkley and Patterson have been pushing each other since Day 1, and that help and competition has been a plus for both players.

"I think Mike is a great player. I try to do the things he does as far as the way he plays technically," said Bunkley. "He is always making plays, always around the ball. He gets in position and he is right there. I'm still learning. Having a guy like that next to me is a plus."

So is having Laws and Klecko in reserve. Both are high-effort players who showed some impressive durability in the preseason logging 40 snaps each game. They are working into the rotation so that everybody is fresh.

The run defense was never poor under Johnson, but it has never been this dominating, either. With a great group of cornerbacks and safeties to work with, Johnson can pressure the line of scrimmage more and take away the running game. And once the Eagles force a team to become one-dimensional and throw the ball, forget about it. The Eagles win in that case.

"You always want to take away the running game," said Bunkley. "We're working on it. We're not there yet, but we're working on it. As long as we push each other and work hard, we'll be fine."

So far, the Eagles have been a lot better than fine. The numbers tell you all you need to know.