SEAN McDERMOTT has faced a few challenges this season, fielding a defense in which five rookies have earned significant playing time. This week, the coordinator's cast gets even younger as the Eagles prepare to visit the Giants, with the Birds planning to throw a sixth rookie into the fray, new starting middle linebacker Jamar Chaney.

"He's prepared all season long. We've got a lot of trust in him. His teammates have a lot of trust in him, the same way. He's worked extremely hard to this point. And he did well in the game the other night," McDermott said yesterday, when asked about the seventh-round pick from Mississippi State.

Chaney's work in practice moved him past veteran Omar Gaither - once a rookie starter for the Birds himself, for part of 2006 - as the replacement for Stewart Bradley, who will miss at least the rest of the regular season with an elbow dislocation suffered Sunday night in Dallas.

How does a rookie, drafted 220th overall, end up starting at a crucial spot for a 9-4 team that hopes to take a huge step toward winning the NFC East Sunday?

"He's got good football instincts and works extremely hard. His play the other night, I think, opened some eyes. If nothing else, it earned the respect of his teammates," McDermott said. "He came in, without many reps in practice, and played good, consistent and above all else, physical football . . . That's a physical team we just played, and the Giants are just as physical as the Cowboys, if not more physical."

Chaney, 6-foot, 242, said that Gaither, standing on the sidelines in sweat clothes after being deactivated Sunday, helped him a lot, "telling me what [the Cowboys] were doing, what to expect, what to do in certain situations."

Gaither said yesterday that Chaney "played well, he played very well" against Dallas.

Despite McDermott's strong support, replacing Bradley with Chaney is a big deal for the Birds' defense. Chaney has played almost exclusively on special teams this season; he said after the Dallas game that he had played in the defense only twice previously, at the end of routs of the Jaguars and Redskins.

"You get so used to being in the huddle or being in your stance and hearing Stew," defensive end Darryl Tapp said yesterday. "With Chaney, I just have to get used to his voice inflections and the way he says things on the field, so I know what voice I'm listening for. There's so much communication going on out there."

Strongside linebacker Moise Fokou, who started eight games last season as a seventh-round rookie, noted yesterday that the middle linebacker "is the quarterback of the front seven. He calls the strength of the formation, he makes all the checks, he lines everybody up, and off what he does, the DBs also communicate. The linebackers, especially the middle linebacker, you're pretty much talking all the way until the ball is snapped, communicating with everybody. It's going to be big for him this week, with me and Ernie [Sims the weakside starter] being in there and knowing what's going on, we should be able to help him, try to make things a little slower for him."

Coach Andy Reid spoke yesterday about how one of Chaney's biggest challenges has been learning how to use his hands to get off blocks. "He wasn't asked to do that in college, but he's worked very hard at that and that's turned into a strength," Reid said.

Chaney, who ran the fastest 40 of any linebacker at the NFL scouting combine (4.54 seconds), said he was able to use his speed to go around blockers in college, but isn't always able to do that here, where there is more emphasis on lane discipline.

"We work on it every day, with the linebackers," Chaney said. "We work on shedding blockers, getting off blocks. That's something [linebackers coach Bill Shuey] has been harping on since Day 1."

Chaney doesn't seem overwhelmed by the moment. He expected to go much higher than the seventh round last spring, and expected to make his mark once he got settled in the defense.

Fokou was asked what we might expect from Chaney.

"Great instincts. Rookie. Bigger guy, bigger linebacker. Powerful," Fokou said. "He's young in the system. He's been learning since camp, but you never really can tell what kind of player he is until he gets on the field and sees the real action."

McDermott was asked why he decided to go with Chaney over Gaither, a former starter who got the nod the last time Bradley was out, Week 2 against Detroit, when Bradley had a concussion.

"Right now, we feel like Jamar is ready to play. We would have the same confidence in Omar we have in Jamar." McDermott said, if anything happened to Chaney.

Gaither has been a starter on the weakside and in the middle, but he has played very little in the defense this year. Since he wasn't even active to play on special teams last week, it is looking like his fifth Eagles season might be his last.

Should Gaither be the one stepping in now?

"I don't know," he said. "It really doesn't matter. This team is on a run right here, down the stretch. I'm just going to support it and do my best to make it win in any way possible. Like I said, Jamar's more than capable of getting the job done. I look forward to watching him."

Gaither said he got no rationale for the deactivation.

"They don't give you a speech," he said. "They just say, 'You're down,' and you say, 'OK,' and you go put on your shirts and your T-shirt."

McDermott said his defense's identity shouldn't change without Bradley.

"To me, we're the same defense, but we'll see," McDermott said. "Any time you have a guy who's not usually a starter in there, [the opponent] usually has a plan, on top of that a rookie. We'll just have to adjust as the game moves forward."

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