Stamina is underrated in the NFL.

Especially if you want to play for Chip Kelly.

As a key cog in the fast-paced offense, and now a veteran with big responsibilities during just his second NFL season, Jordan Matthews knows how important it is for the Eagles to practice well, get faster and build the stamina to be able to play a full 60 minutes in the fall.

"The speed of the game, it kind if picks up," Matthews said. "And fatigue picks up too. It's the offense, it's very fast. Most teams they just do two minute drills sometimes, we do that every period. It's a different kind of shape you've gotta be in."

Matthews clearly has gotten himself into perfect shape for the Kelly offense, tallying 872 yards on 67 catches last year. Many expect him to finish 2015 much closer to 1,200 receiving yards -- or more.

He may hail from Alabama, by way of Vanderbilt but Matthews says he is the embodiment of everything Philly. Which acts as a great motivator as he looks to improve in year No. 2.

"We are blue collar," Matthews said. "We have to go out and grind it out. We aren't worried about different opinions, what we need and what we don't have."

All Matthews and the rest of the Eagles receiving corps can do is focus on the work at hand. And for the Eagles under Kelly's regime, the work at hand is getting stronger and building more stamina.

"As the game goes, on, routes aren't as crisp as the first quarter," the receiver said. "Being able to stay in shape and pay a full game, it can help you. When the game is on the line, sometimes technique goes out the window and you've gotta just be a beast."

The sports science program practiced at the NovaCare complex is a good compliment to what the Eagles are trying to do this year. Go even faster.

"If you know better, you do better," Matthews said. "I think sometimes football is such a blue collar sport, people want to push through -- and say 'it's football.' These guys are tough but they don't have to prove themselves anymore, it's the NFL... luckily we have a coach who wants to put as much effort into that as Xs and Os."