PHILADELPHIA (973espn.com) - First day, first injury. And it's a significant one.

Eagles backup middle linebacker Paul Worrilow suffered a torn ACL during 7-on-7, red-zone drills Tuesday when the veteran collided with fellow LB Corey Nelson while trying to defend an underneath throw from Nate Sudfeld to Donnel Pumphrey.

Worrilow, a Wilmington native who signed with the Eagles in the offseason, went down in obvious pain while clutching at his right knee. He immediately slammed the turf as trainers raced toward him.

Both head coach Doug Pederson and LB coach Ken Flajole looked on as an aircast was applied to Worrilow's leg before he was carted out of the team's practice bubble.

Worrilow has been working with the second-team nickel group before going down.

"All three of us collided," Nelson told 973espn.com after practice. "His leg kind of whipped around and hit my back."

DAY 1 OTA OBSERVATIONS:

-The defense seemed to get the better of the offense for most of the session. On one occasion things broke down and Mike Wallace sped downfield but a Nick Foles heave was badly underthrown and picked off by Jalen Mills.

Sidney Jones also pocketed a nice INT while undercutting Nelson Agholor after Foles was pressured by Fletcher Cox. Meanwhile, De’Vante Bausby, a practice squad player last year, picked off Nate Sudfeld while shadowing rookie tight end Dallas Goedert in red zone work.

-Speaking of Jones, he was the first-team nickel back with Mills staying outside and left corner and Darby handling the right side. Rookie fourth-round pick Avonte Maddox, who played outside at Pitt, was getting most of his work in the slot and embraced the move after practice.

"You need to understand a lot more as far as option routes and run support but it only helps you become a more well-rounded player," he told 973espn.com. "I'm excited."

Bausby, a lengthy 6-foot-2 corner, got work with the second team on the outside at LC.

-South Jersey's Joe Callahan found 6-foot-4 WR Marquess Wilson in the corner for a TD during 7-of-7 red-zone work.

-Like Wentz, Jordan Hicks, who is returning from a torn Achilles, did a lot of work in individual drills and was even mixing in during group install before sitting out team work.

-With Brandon Graham recovering from recent ankle surgery and Michael Bennett skipping the session, Chris Long and Derek Barnett were the starting defensive ends so Barnett is already recovered from his sports hernia surgery. Fletcher Cox and Destiny Vaeao were the tackles.

-Tre Sullivan and undrafted rookie Jeremy Reaves were the backup safeties behind Malcolm Jenkins and Rodney McLeod.

-As expected Donnel Pumphrey looked very good in the non-padded environment similar to last season, flashing impressive quickness which really stood out.

-Undrafted free agent DE Joe Ostman showed impressive burst as a pass rusher from the left side.

-Isaac Seumalo was working as the center in 7-on-7 drills.

-LB Mychal Kendricks was seen leaving the building before practice and was released after practice.

-Rookie sixth-round pick Matt Pryor worked at both right guard and right tackle with the second and third teams while Jordan Mailata was stationed at LT behind Halapoulivaati Vaitai. Jason Peters was doing individual work and group install but no team drills. Seumalo only worked in 7-on-7s as the center. Jon Toth was the second-team OC in team drills and there was some struggling with the exchange at times.

QUOTE OF THE DAY:

The 6-foot-8, 346-pound Mailata, the fromer Aussie rugby player trying to make the transition to NFL left tackle, joking about hard-nosed position coach Jeff Stoutland:

"Stout is the father figure you never wanted."

Second-year WR Mack Hollins on the Eagles' embarassment of riches at QB:

"The guy who should have been the MVP [Carson Wentz], the Super Bowl MVP [Nick Foles] and the future MVP [presumably Nate Sudfeld and not South Jersey native Joe Callahan].

-John McMullen covers the Eagles and the NFL for 973espn.com. You can reach him at jmcmullen44@gmail.com or on Twitter @JFMcMullen

Want more NFL? Check out John's piece on why the comparison between Jared Goff and Mitchell Trubisky needs a little more nuance at GetMoreSports.com.