ZACH ERTZ was as excited as an 8-year-old on Christmas morning.

After an MRI showed that the rib displacement that had sidelined him for the last two games had completely healed, the Eagles' fourth-year tight end eagerly returned to the practice field Monday to prepare for Sunday's game against the Detroit Lions.

"Honestly, every day not being out here at practice, not being in the games, was killing me," Ertz said. "Not even being able to travel to Chicago (for the Eagles' 29-14 Week 2 win over the Bears on Monday Night Football) killed me.

"It was really tough. Very eye-opening. Everyone knows the story of Wally Pipp. I don't think that was going to happen. But at the same time, everybody understands the possibility in this league.

"And it's tough not being out there with your guys, your brothers. You work so hard. But at the end of the day, it was only two games. And the team played really well. And that's all that matters."

Ertz is one of the league's top pass-catching tight ends. He had six catches in the Eagles' season-opening win over the Browns, including four for first downs, before suffering the freak injury.

Amazingly, the offense didn't miss a beat without him. The team's other two tight ends, Brent Celek and Trey Burton, did a terrific job of picking up the slack as the Eagles scored 63 points in wins over the Bears and the Steelers for just the ninth 3-0 start in franchise history.

Celek, one of the best blocking tight ends in the NFL, is averaging 18 yards per catch, and Burton, who theoretically would be Lou Gehrig to Ertz's Pipp, has seven catches for 68 yards and a touchdown.

Sunday will be the first time the Eagles will have all three of their tight ends on the field together. Burton missed the season-opener against the Browns with a calf injury.

That's significant because the Eagles plan to put Ertz, Celek and Burton on the field together a lot this season.

Most teams usually only use three-tight-end sets to provide extra run-blocking help in short-yardage and goal-line situations. But all three of the Eagles' tight ends are excellent receivers, which is going to keep defenses guessing and create matchup problems.

"We have three really talented tight ends," Ertz said. "Three of the best in the league. All offseason there was a lot of work put into that (three-tight-end) package. It's going to grow this week because all three guys are going to be able to catch passes. No offense to Matt (Tobin, backup offensive lineman).

"So we're real excited about that package. We think it's going to open up everything else, in the run game and the pass game."

Even without Burton in Week 1 and Ertz in Weeks 2 and 3, coach Doug Pederson's enthusiasm for three-tight-end personnel groupings has been evident.

With Tobin serving as the third tight end, the Eagles used three-tight-end sets on 28 of 202 plays in the first three games - 26 times with "13" personnel (one running back) and two times with "23" personnel (two running backs). That's the same number of times Chip Kelly used three-tight-end sets.

In three SEASONS here!

Just four of those 28 plays were pass plays - including a 22-yard completion to wide receiver Jordan Matthews, and a 2-yard touchdown pass to Burton, both against the Bears.

"(Three-tight-end sets) helps you obviously in the run game because you've got bigger bodies protecting the edge," Pederson said. "But with Trey, Celek and Ertz in there, it creates a little bit of a matchup (problem) for defenses."

Defenses really can't afford to play nickel against a three-tight-end look because replacing a d-lineman or linebacker with a defensive back would leave it susceptible to the run.

But if it stays in base against Ertz, Celek and Burton and, say, Matthews and Darren Sproles, there are going to be some coverage mismatches.

"They'll stay in base against three tight ends," center Jason Kelce said confidently. "We'll see base personnel. But if you stay in base, we can compromise them in the passing game. If you go to nickel, obviously you'll have some lanes to run the ball. It's a nice predicament to put a defense in."

Ertz agreed.

"It's tough to go nickel against three tight ends," he said. "But if teams go base, or possibly even bigger packages, then we have the ability to spread Trey and I out.

"If you have three really good tight ends who can do both (block and catch the football), which, in our opinion, we can - you'd have to ask (Eagles defensive coordinator Jim) Schwartz how he would game plan for it. But in our eyes, I think it presents a lot of problems."

Schwartz isn't sure how he would game plan for it because it's not something he has to worry about. There isn't another offense in the league that has three tight ends who possess the blocker-receiver versatility of Ertz, Celek and Burton.

"If you have three guys that are just stone-cold blockers and they can't run a route, it's pretty easy to defend," Schwartz said in August. "And if you have three guys that are (strictly) pass receivers and can't block a soul, it's pretty easy to defend.

"But if you have guys that can do both and they can give you a lot of different looks and they can be in three tight ends, it might be a short-yardage-looking offense or it might be a three-wide-receiver-looking offense.

"All three of those guys have the capability of being (both). It just forces you to be able to match up."