After Brent Celek sustained a concussion on the first play from scrimmage of Sunday's win over the Tampa Bay Buccaneers, Clay Harbor took his place at tight end. The Eagles didn't call his number right away. They eased him into the offense with a few protection assignments. After a few snaps, tight ends coach Tom Melvin called down from the press box to speak with Harbor.

"I'm fine now. I'm in the game. The jitters are gone. I'm going to have a good game," Harbor told Melvin.

After the game, Melvin reminded Harbor of that conversation. Harbor did indeed settle down, and he played 67 percent of the Eagles' snaps to finish with six catches for 52 yards and an 11-yard touchdown reception. Harbor caught every pass thrown in his direction.

Harbor will continue as the top tight end on Thursday against the Cincinnati Bengals. Celek has already been ruled out, meaning Harbor, a third-year tight end, has his best chance yet to prove his worth.

"You can't really replace Brent Celek," Harbor said. "It's an opportunity for me to get on the field more and get more snaps, and really build confidence in the coaching staff and put some stuff on film there and show them what I can do. I'm going to take it as a good opportunity to get out there and get some good playing time."

Harbor has played in every game this season, although he has not filled the role that seemed possible during the preseason. The Eagles were intrigued by the idea of playing two-tight end sets, and they opened the season that way. Harbor was targeted six times in the season opener and caught the game-winning touchdown.

He played more than 30 snaps during the first two weeks before his snaps started to decrease. One of the main reasons for the decrease was the Eagles were so often playing from behind. They utilized the two-end formation less frequently when they were in comeback mode, and that affected how much Harbor played during the eight-game losing streak.

"I probably did expect to get a few more snaps, but it all comes down to game plans and what we get from defenses and what happens during the game," Harbor said. "If we get down by a couple of scores early . . . we stop going to two-tight end, one-running back sets. We start spreading the ball around to try to move the ball down the field faster."

Harbor plays one of the few positions on offense that had not been hit by injuries. The only starters on offense to play every game this season are Celek, guard Evan Mathis, and fullback Stanley Havili.

Celek tops Harbor on the depth chart, and the Eagles seldom play two tight ends and two running backs at the same time. So Havili's presence also affects Harbor.

With Celek out, Harbor is just one of the Eagles' key young players who are seeing playing time. Rookies Nick Foles, Bryce Brown, Dennis Kelly, and Dallas Reynolds are all starting due to injuries to starters. The Eagles will open a roster spot for another tight end and likely move a player up from the practice squad for Thursday's game.

Even though Harbor is in his third season, his inexperience means Thursday is a learning opportunity. Celek met with Harbor to help him prepare, and Harbor knows there are elements of his game that must improve. But like he told Melvin, the jitters have faded, and he's ready to play.

"I've got to get better in protections in the run game, even run some routes better," Harbor said. "It will be my first start, so it's pretty exciting."

Young Guns Under the Gun

Young Eagles replacing injured veterans

POS.   IN   OUT

QB   Rookie Nick Foles   Michael Vick (concussion)

RB    Rookie Bryce Brown   LeSean McCoy (concussion)

C   Rookie Dallas Reynolds   Jason Kelce (knee)

RT   Rookie Dennis Kelly   Todd Herremans (ankle)

TE   3d year Clay Harbor   Brent Celek (concussion)

Concussed Eagles

Players who have suffered concussions this season

QB Michael Vick

RB LeSean McCoy

TE Brent Celek

WR Riley Cooper

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Contact Zach Berman at zberman@phillynews.com. Follow on Twitter @ZBerm.