With Steve Spagnuolo off to New Orleans, and an Eagles contingent of coaches and scouts expected to be in nearby Mobile, Ala., on Monday for Senior Bowl practice, it's starting to look as if the Eagles have settled on a defensive coordinator.

He has prior experience as a coordinator. His defense ranked eighth-best in yards allowed and 10th in points surrendered last season.

Yes, Eagles fans, meet your (not-so) new defensive coordinator - Juan Castillo!

A tire deflates. A balloon pops. Someone loses on "The Price Is Right."

 OK, so the return of Castillo isn't likely to excite a downtrodden fan base. Castillo's learning curve likely cost the Eagles at least one game last season. His zones were often convoluted, his play-calling a step behind. And even a late-season rally was fool's gold, to steal a phrase.

But what if the large majority of fault lies elsewhere? What if the Eagles' problems on defense were systematic and it didn't matter if Juan Castillo, Steve Spagnuolo, or Bud Carson was devising the scheme and calling the plays?

What if the Eagles' problems on defense were related to Reid's preference for drafting and acquiring smaller players? The argument could be made that Reid and his recent general managers - Tom Heckert and Howie Roseman - just haven't been very good at drafting players on that side of the ball.

But as the Eagles have shrunk on defense over the last three seasons, the results have gotten worse. They've finished 12th, 12th, and eighth in total yards and 19th, tied for 21st, and 10th in points allowed since 2008. Those numbers aren't bad by any means, but they don't tell the whole story.

This season there were five blown leads in the fourth quarter; a lack of forced turnovers; and, for the third straight season, a horribly inefficient red-zone defense. Could it be that a lack of size both vertical and horizontal contributed to the troubles in those areas?

Giving a definitive answer to that question is difficult. But make no mistake about it, the Eagles are small. Taking into account a possible margin of error in deciphering depth charts and assuming every team fibs on its measurements, the Eagles' starting 11 is the shortest in the NFL, and only two other defenses are lighter.

The Eagles' average starting defensive player stands 6-foot-3/4 and weighs 240 pounds. The league average is 6-11/2 and 246.3 pounds. Because 3-4 defenses are generally larger than 4-3s - of which the Eagles are one - the disparity isn't as great when compared to teams that use a four-man front.

The average size of the league's 17 4-3 defenses is 6-11/2, 244.5 pounds; of 15 3-4 defenses the average is 6-13/4, 248.3.

Still, anyway you slice it the Eagles are tiny, comparatively speaking. But does size matter? A look at the remaining four teams in the playoffs would suggest it does, although the old adage that defense wins championships may not ring as true as it once did.

The Ravens are the heaviest team in the NFL at 255 pounds. The New York Giants are the tallest at 6-31/2. The Patriots are the second-heaviest 4-3 defense at 251 pounds. Only the 49ers (6-11/4, 245) are below average among the four.

What about the eliminated playoff teams? Of that group some tip the scales, some don't. The Texans (6-21/4, 250), Packers (6-11/2, 251), and Bengals (6-11/2, 247) are on the larger side. The Steelers (6-1, 244), Broncos (6-1, 242), Lions (6-1, 240), Saints (6-03/4, 242), and Falcons (6-11/4, 239) are on the smaller end.

Is there any correlation between size and regular-season success? Yes, but in some cases no. The Texans, Ravens, and New York Jets (6-2, 250) are three of the bigger defenses and finished second, third, and fifth in total defense. The Bengals are large for a 4-3 team and ranked seventh. But the Steelers and 49ers are small for 3-4s and were Nos. 1 and 4 in total defense.

Too much can be made of yards. What about points allowed? Generally, the teams that ranked high in total defense were among the leaders in points surrendered. The Seahawks (6-2, 254), Browns (6-11/2, 254), and Dolphins (6-21/2, 253) were three of the bigger teams and finished seventh, fifth, and sixth in points allowed.

The Packers, Giants, and Patriots were not strong in either category, but they ranked tied for first, tied for fifth, and tied for fifth in forced turnovers. Overall, though, there appeared to be no link between size and turnovers, at least based off this season.

But there was a connection between size and red-zone performance, where the field contracts and speed doesn't matter as much as having big and tall defenders. The Ravens, Cardinals (6-21/2), Browns, 49ers, Redskins (6-13/4, 247), and Dolphins were the top six red-zone defenses.

The Bills (an average 3-4 at 6-11/2, 248), the Colts (6-3/4, 237), Eagles, Chargers (another average 3-4 at 6-1, 246), Saints, and Panthers (6-1, 242) were the bottom six.

You have to also wonder if those five fourth-quarter collapses had anything to do with the Eagles' being undersize and beaten down.

"On defense, I like fast players and like guys that can run and play fast," Reid said last year before the draft. "Size - I don't really necessarily get too caught up on the size. I care about playing strength and speed and quickness."

If Reid is indeed staying with Castillo, it's difficult to imagine his bending on the defensive players he covets.