Falling stars puzzle Dallas Cowboys

IRVING, Texas -- These guys aren't Bobby Carpenter-like busts.

Outside linebacker Anthony Spencer, running back Felix Jones and cornerback Mike Jenkins were major contributors for the NFC East champion Dallas Cowboys last season. The recent first-round picks all seemed on the verge of stardom.

That's what makes their performances this season so puzzling and problematic. The rising stars have regressed significantly after their breakout seasons, making them part of the problem for the NFL's most disappointing team.

"It's a regression for our team overall," coach Wade Phillips said, refusing to single out his former first-rounders.

OK, so their mediocrity has plenty of company. The drop-offs for these promising players have been drastic.

This isn't about hoping the Cowboys' scouting department correctly identified first-round talent. Jones, Jenkins and Spencer demonstrated their ability last season, especially down the stretch. They established a standard that they aren't coming close to reaching this season.

Jones and Spencer have been just average for the 1-6 Cowboys. Jenkins has been awful.

Jones, who had flashes of brilliance in between injuries his first season and a half, showed late last season that he was capable of excelling as a lead back. He rushed for 475 yards (6.0 per carry) and two touchdowns in the last six games of the season, including the playoffs. Compare that to his pedestrian numbers through seven games this season: 286 rushing yards (4.2 per carry) and no touchdowns.

If you subtract Jones' lone 100-yard performance, he's averaging only 3.3 yards per carry. That's not exactly a number that keeps opposing defensive coordinators up at night.

It's hard to determine how much an offensive line in need of an overhaul is at fault for Jones' struggles. But he definitely doesn't get off the hook. He reported to training camp at 220 pounds, heavier than ever before, and admits that conditioning has been an issue. (He vomited at halftime of the loss to the Minnesota Vikings.) He appears to have lost explosiveness, although Jones and his coaches won't acknowledge that.

Jenkins seems to have lost his swagger, which is the worst thing that can happen to a cornerback other than injury.

He's been flagged an NFL-high five times for pass interference, costing the Cowboys 89 yards. And he hasn't had much success when playing within the rules, either.

According to Stats Inc., teams have completed 21 of 34 passes for 373 yards against Jenkins, who has just one interception. That's an off-the-charts 11 yards per attempt -- almost double the figure against Jenkins in 2009, when he had five interceptions and was picked as a Pro Bowl alternate.

Jenkins readily admits that he isn't pleased with the way he's playing. He doesn't say much else these days.

"I need to let my play talk for me," Jenkins said.

Teammates spoke of Spencer as being the defense's most dominant player in the second half of last season, quite a statement considering the presence of All-Pro DeMarcus Ware on the other side of the field. Spencer had eight sacks in the last eight games, including the playoffs, and wreaked havoc against the run all season.

Spencer's stats this season aren't very impressive, as is the case for the Dallas defense as a whole. He has three sacks and only one tackle for a loss.

While Spencer doesn't believe he's hurting the team, he acknowledges he's frustrated with his lack of production.

"I still have the same expectations," Spencer said. "We have nine games left. Still have a lot of time left to reach the goals I have."

Barring a miracle, it'd be too little, too late for this season.

But Jones, Jenkins and Spencer haven't even hit their primes yet. Is this season just a particularly painful speed bump for the former first-round picks?

The Cowboys' front office certainly hopes so. These players are significant pieces of the Cowboys' foundation for the foreseeable future, for better or worse.

Tim MacMahon covers the Cowboys for ESPN Dallas. You can follow him on Twitter or leave a question for his weekly mailbag.