Is the Cowboys' defense just not good?

Tim MacMahon of ESPNDallas.com has a column up, and it's about the Dallas Cowboys' defense. Specifically, it's about first-year defensive coordinator Rob Ryan, who Tim says is struggling to coach something out of the same cast of characters that helped get the previous coach and defensive coordinator, Wade Phillips, fired a little more than a year ago.

Tim's hypothesis is that maybe it's not the fault of the coach or the scheme in Dallas, but that maybe we've all been overrating the players the Cowboys have on the defensive side of the ball:

The truth is that this defense has three cornerstone players -- outside linebacker DeMarcus Ware, nose tackle Jay Ratliff and inside linebacker Sean Lee -- and a whole bunch of question marks. Throw a dart at the defensive depth chart and you're pretty much guaranteed to hit a draft need.

Cornerback Mike Jenkins has first-round talent and deserves credit for fighting through injuries all season, but he's on-again, off-again. Outside linebacker Anthony Spencer, another former first-round pick, has flashes of brilliance that are lost in long stretches of mediocrity.

Cornerback Terence Newman is way past his prime and looks like he's on his last legs after a few weeks of actually playing well enough to earn his massive contract earlier this season. Inside linebackers Bradie James and Keith Brooking are tough, old warriors whose glory days are long gone.

The rest of the defense is filled with JAGs, to borrow a term from Bill Parcells. The just-a-guy list includes safety Gerald Sensabaugh and [Orlando] Scandrick, even though they've been given five-year, $20-plus-million contract extensions this season.

It's an interesting point, for sure. Two years ago, when the Cowboys turned it on this time of year and won a division title, Spencer and Jenkins played like stars. They have not done so since, and as a result there are very few players on the Cowboys' defense who are. It's one thing when you have five or six guys playing like stars. It's quite another when you have only two or three.

The theory behind hiring Ryan was that the Cowboys underachieved on defense last season and needed a fresh voice to coax the talent out of all the talented players they already had in place. And while he's been able to get something out of Spencer and Jenkins (and, earlier in the season, Newman) that wasn't there a year ago, Tim's right that none of those guys is playing at a star-caliber level. Can they the rest of the way? Sure. We've seen it before for brief stretches with some of these same guys. But once this is all over, it seems the Cowboys are going to have to make some more serious and sober assessments of just what exactly they do have on defense.