PHILADELPHIA (AP) - Casey Matthews has been through training camp, the preseason games and all the hype surrounding his status as the Eagles starting middle linebacker.

On Sunday, it actually happens.

I'm really excited,'' Matthews, a fourth-round draft pick out of Oregon, said.And I'm obviously looking forward to the opportunity of playing in a game that really matters. The preseason matters, but these are the ones that count.''

When the Eagles travel to St. Louis for Sunday's season opener against the Rams, Matthews will be in the middle of an Eagles linebacking trio that is both young and inexperienced.

Second-year linebacker Jamar Chaney, who started three games including the wild-card playoff loss to Green Bay in the middle last year, is now on the strong side. And third-year linebacker Moise Fokou, who has 15 career starts, most of them on the strong side, is the starter on the weak side.

That's a total of 18 NFL starts for all three linebackers combined. And none for Matthews.

I feel I progressed pretty well through camp,'' he said.We didn't have the OTAs and the minicamps, because of the lockout, so it was tough coming in Day 1 and trying to run the defense. Now, I feel more comfortable, and the more reps you get, the more comfortable you feel. Things are starting to slow down and I'm starting to learn what other people are supposed to do out there besides my position. I feel like it's all coming along.''

Matthews' debut comes against a rebuilding team that has its sights set on winning the NFC West this year. The key to the Rams, as it has been for the past several years, is running back Steven Jackson.

Last year, he finished seventh in the league with 1,241 yards. And this year, his presence in the backfield is paramount to the success of second-year quarterback Sam Bradford.

He's the focal point for us,'' Matthews said of Jackson.He's one of the premier backs in the league. He's the one who makes them go. You want to try to make them one dimensional if you can. If you let him get going it makes things a lot easier for Sam.''

The Eagles are trying to make things easy for Matthews, the brother of Clay, a Pro Bowl linebacker with the Packers.

Casey has done a nice job,'' coach Andy Reid said.What you saw with Casey was improvement every game that he played and Juan (Castillo, the defensive coordinator) hasn't slowed down with him. He's asked him to be the primary signal caller, he attacked that innate learning ability of his and tested it.

``Casey was able to retain and make all the calls, and still, at the same time, get better every week playing football. And that's a tribute to the kid.''

NOTES: Quarterback Vince Young took a few snaps at practice yesterday, but is still listed as doubtful for Sunday. If Young can't go, Mike Kafka will be the No. 2 behind Michael Vick. ... Cornerback Asante Samuel tweaked his shoulder in practice on a collision with receiver Riley Cooper. Samuel appeared to be OK, but was listed on the injury report as probable. ... Receiver Steve Smith, who suffered a microfracture in his knee while playing for the Giants last year, has made it all the way back and will play Sunday. I really didn't know what to expect, but I had my doubts,'' Smith said.I had heard nothing but bad things about the injury. To be able to play opening day, it just feels great.''