Arrelious Benn could be a starting wide receiver for the Eagles on opening day - or he could be off the roster by then. It's hard to find a player with as many variables as Benn, the talented 24-year-old wide receiver who was acquired by the Eagles in March.

One of Chip Kelly's maxims is that "durability is the best ability," which would not seem to be a point to ponder for Benn. He's a former second-round pick who has the size (6-foot-2, 220 pounds) and the ability to be a productive NFL receiver, except for that part about durability.

He missed at least one game in each of his three NFL seasons with the Tampa Bay Buccaneers, leading to his falling out of favor despite his age and talent.

"I've got to stay healthy," Benn said Sunday. "If I can prove to them I can stay healthy, I'll be all right."

It didn't help Benn's case that on the first day of Eagles camp, he hurt a knee. He left the July 26 practice and did not return until Sunday, a span that included six practices with Benn watching from the sideline. During that period, Jeremy Maclin was lost for the season with a knee injury and Riley Cooper was lost for the foreseeable future.

"Football's all about opportunity and timing," Benn said.

Benn has the perfect opportunity to become a major part of the offense, but the timing of his injury was not good. He must show the Eagles that he can stay healthy for them to depend on him.

"Absolutely," Benn said. "That's something I dealt with in Tampa. Coming up here, knowing all the little things I need to know as far as staying on top of my body, it's kind of funny I went down the first day because I went down last year the first day in Tampa. I know how to handle it as far as getting my mental reps when I'm not out there."

Kelly said Benn's injury history would not be a factor in the receiver's evaluation. But Benn must play for the team in order to be evaluated, and Sunday was his first full practice of training camp.

"We've just got to take him the way he is," Kelly said. "Obviously, he's had some injuries in his career."

The coach said he was "pleasantly surprised" by how Benn looked in practice. He expected Benn to ease back into the offense, but he thought the receiver looked "really good from a mental standpoint."

"At this point in time, he's been in the league for a while, he's an experienced player, so what can we use him for?" Kelly said. "Right now, with his size, his ability to play special teams, he can bring a lot to the table."

Benn said he was not frustrated during his recovery, although he conceded that "two days felt like a week." The injury lingered longer than anticipated, yet Benn did not miss any games, and there were two off days during the eight-day interval. Benn said the injury did not set him back in learning the playbook because he had been with the team in the spring.

Benn took snaps with the third-team offense. As much as Kelly insists that the depth chart does not matter, it was telling when undrafted players such as first-year receiver Ifeanyi Momah and rookie Russell Shepard superseded him. Benn missed time when the Eagles inserted the offense, and Kelly said that the team called plays Sunday that the receiver had never run before.

"I was supposed to hold back to less than what I did today, but I just couldn't," Benn said. "I was in there; I had to do what I had to do, just see how I felt. This was a day to see how I felt."

Benn will be a key player to watch during the next month, especially because Cooper's situation is unsettled. The Eagles wide-receiver corps is open beyond DeSean Jackson and Jason Avant, and Benn is the most accomplished - and perhaps even the most talented - of the other receivers. The question is whether he can prove durable.

"I'm not concerned about that," Benn said.

Contact Zach Berman at Follow on Twitter @ZBerm.