There is nothing funny about injuries, but injuries are a funny thing when it comes to evaluating how a coach or a team is performing. Are there enough injuries to key players to grade on a curve? Or is it still possible to judge a coach's plan and a team's execution of that plan in spite of whatever injuries have been endured?

In the Eagles' case, for now at least, injuries do not excuse the so far disappointing 2009 season. The best place to begin this discussion is where most football matters begin: on the offensive line.

The Eagles have been juggling linemen all season. Shawn Andrews never played a down at right tackle. Jason Peters has missed time at left tackle. Todd Herremans was hurt early and has played both at left guard and left tackle. Max Jean-Gilles and Stacy Andrews have rotated at right guard - at least partly, we are led to believe, because Andrews is not all the way back from his reconstructive knee surgery.

"I want continuity among the offensive line," Eagles coach Andy Reid said yesterday. "I'm fortunate enough to guys who have played here and have experience in this league, but on the other hand, I'd like them to play together a little bit more than what's gone on. I don't expect that to be an excuse, by any measure."

And it isn't an excuse, because the root problem is the decision-making that led the Eagles to this point. Faced with moving on from bookend tackles Tra Thomas and Jon Runyan, Reid and his advisers put all their chips on the Andrews brothers and their friend, Peters. It goes without saying that this has proven to be a bad and expensive strategy.

Shawn Andrews is out with the same injury he had last year. Stacy Andrews is struggling with an injury everyone knew he had. And Peters has shown exactly how invaluable the reliable Thomas and Runyan really were.

But go back even further. Reid took this route because he didn't trust Winston Justice, Jean-Gilles, Nick Cole, and Mike McGlynn - all linemen who have been drafted (besides Cole) and developed for two to four years. It is bitter irony that those guys are now forced to play because the multimillionaires aren't able, or aren't as good.

Reid has always recited a mantra about injuries to his backup players, and he repeated a version yesterday.

"You get in, you better know your assignment, you better play physical football and you better take care of business," Reid said. "Those are opportunities for you."

It is a fine message to send backups. You need them to prepare as diligently as the starters, just in case they play. And you want them to step onto the field with confidence.

But that's for the players. The coaches have to know better and react accordingly. One of the Eagles' problems, at times, is that Reid practices what he preaches. He will game-plan and call plays about the same, no matter who's missing and who's filling in.

The most glaring example was the night Justice had to fill in at left tackle for Thomas at Giants Stadium two years ago. Reid has recently acknowledged that he should have made adjustments to account for Justice's inexperience. But that shouldn't have taken two years to figure out. It seemed obvious in real time to everyone watching Osi Umenyiora abuse Justice (and therefore Donovan McNabb).

So when the offensive line isn't quite clicking in San Diego, maybe it's a bad idea to run up the middle twice from the 1-yard line. More pertinent now, rookie running back LeSean McCoy is going to have to play in place of Brian Westbrook on Sunday in Chicago and probably for much, much longer.

The concern is that Reid and Marty Mornhinweg will decide the best way to attack Chicago's defense (which is better against the pass, as if that means anything) is to throw on every down, and that McCoy will be tested with new blitzes every time he's out there.

Part of coaching is knowing your players' - and your own - limitations and managing accordingly. The Eagles have too much at stake this week to figure out McCoy's two years too late.

Every team has injuries. The ones who plan and adjust as needed have a chance to overcome them. The ones who don't have the chance to be 5-5 in the middle of November.

Contact columnist Phil Sheridan at 215-854-2844 or psheridan@phillynews.com. Read his recent work at http://go.philly.com/philsheridan.