PHILADELPHIA -- Cullen Jenkins could not believe what he was seeing or hearing. It was halftime in the Philadelphia Eagles' locker room Sunday, and while they were up 20-3 on a dead-looking San Francisco 49ers team, to Jenkins' eyes and ears it appeared as though the game already had been won.

"I think it was a little bit too happy in here," said Jenkins, who won a Super Bowl with the Packers last season before signing with the Eagles in the offseason. "Just because you've got a lead in the game doesn't mean you've played a good game."

A couple of hours later, Jenkins and the rest of the Eagles stood in front of their lockers trying to explain how that 20-3 lead had evaporated into a 24-23 loss, and how a team for whom preseason expectations were so high is a pitiful 1-3 after four games. The Eagles have lost three straight games in which they held fourth-quarter leads, and the only good news for Eagles fans is that at least someone in the room is embarrassed about it.

"The biggest thing we're missing in here is the attitude," Jenkins said. "There's not that fire, that mental toughness that makes you think you're going to make it happen. And we've got to get that. At some point, the man in you has to come out."

But after the third straight game in which a defense in which so much was invested has given away a lead, it's fair to wonder if that will happen at any point this season for the Eagles. They can sit there and claim their errors are correctable, but I'm not sure they're right. Is Jeremy Maclin going to start taking care of the ball better when he runs? Are the Eagles' defensive backs going to start using their arms to actually wrap up ball carriers and bring them to the ground? Are the linebackers going to get faster and more alert? Are the coaches going to figure out that, just because you're inside the five-yard line you're not automatically in the end zone yet? And even if one or two of those things happen, will all of them get fixed?

The issues with this Eagles team run deep and fundamental. They don't tackle well. They don't grind out extra yards under tough circumstances. They don't beat up the other team physically. They can make big, showy plays, sure. Their quarterback and their receivers and their pass-rushers are all capable of making you hop out of your seat with excitement. But the Eagles aren't big on the kind of solid, boring football plays that win games when you stack them all on top of each other -- especially once you have a big lead.

"You can't sit on leads," Eagles coach Andy Reid said. "You can't do that as a football team. That's what I did with our team here, and we lost the game."

Coach Andy Reid and the Eagles are now 1-3 overall after losing 24-23 to the 49ers. AP Photo/Julio Cortez

This is a big part of Reid's act -- sitting there after the game and owning up to the loss. Sometimes, it's as if he's reading off a script. But after a while, it starts to ring hollow -- as if he's saying this stuff because he knows it's part of the head coach's job to say it. Fact is, he's not the one missing tackles or fumbling or failing to pick up a blitzing linebacker. He should not be free from blame, of course, but the Eagles' problems are far more basic than schemes or play calls. The Eagles, for all of the dazzling talent they have on both sides of the ball, don't play football very well. And I'm not sure that's something the Eagles' coaching staff, for all of its own considerable talent, can fix in 12 weeks.

"Right now, we all hurt," said embattled rookie defensive coordinator Juan Castillo, the current target of a significant part of Eagles fans' significant scorn. "But we've been in this situation before. We have a plan, and we'll stay with our play, and if we do that, we'll turn it around. We always have."

Eh, sort of. There are a handful of examples, in the Reid era, of the Eagles starting slowly and recovering. They were 2-3 in 2008 and finished 9-6-1. They were 1-3 in 2007 and finished 8-8. And they were 0-2 in 2003 and finished 12-4. But the problem here is that the Eagles' coaching staff doesn't -- and can't -- know what kind of men it has in the locker room. They can't know if it'll get better because this group hasn't played together, doesn't have anything in the bank that proves it can handle adversity and get back on its feet. We don't know if Nnamdi Asomugha can handle the pressure of this opportunity and start making tackles.

"There's a lot of talented teams around the league that never win, and it's because they don't learn how to play the game as a team," Jenkins said.

Jenkins says it can happen -- that he saw his Packers team go through that transformation and toughen up because the players in the locker room got sick of losing games they should have won. The question with this Eagles team is whether enough of the players will get sick of it, and whether that'll happen in time to save this very important Eagles season.

"It's not good," Asomugha said. "It's not good right now."

But the question is whether things are bad enough, or embarrassing enough, to motivate the Eagles to do better. With 12 games to go and the division clearly still winnable, the Eagles will have a chance to turn things around. They clearly have the talent to do it. Right now, it's a matter of how badly they want to.

"There's got to be a point where people step up and say, 'We're going to play a full four quarters,' " Jenkins said. "It's like people in here don't have a sense of urgency. That killer mentality: Some people have it and others don't, and we've got to get it."

Unfortunately, that's not something you can go out and sign on the free-agent market. Or else the Eagles surely would have tried.