THE KEY to Ryan Mathews remaining healthy might just lie in an analogy between beef jerky and an uncooked steak.

Beef jerky is dry and easy to pull apart. But a good piece of meat, fresh out of the package?

"Try and pull that apart and it's a lot harder," Mathews said.

Mathews was waxing poetic about hydration after yesterday's minicamp session. And he referred to the analogy shown to the team in a slideshow during a meeting. Hydration, Mathews said, was something he never thought about before this year.

And, surely, he didn't really think of his body as a raw filet mignon, either.

"You've got muscle fibers and stuff that's protecting your joints . . . that's really going to go a long way for me," he said.

The running back the Eagles signed to replace LeSean McCoy - before eventually bringing in the NFL's leading rusher, DeMarco Murray - has a long line of injury history.

But now, Mathews is learning - like so many in coach Chip Kelly's system do - a little bit about sports science and staying healthy.

"There's a lot of unknowns coming into here with my health and stuff," said Mathews, who was drafted 12th overall by San Diego in 2010 out of Fresno State. "I didn't know a lot. I thought just working out every day and making sure I'm in shape and strong and stuff was the main focus. Now that I look back on it, I was very, very dehydrated. That was one thing that I never really focused on.

"I thought I could just drink a couple a bottles of water the night before the game, a couple bottles of water before the game and be all right. That's not even the case. The hydration process starts days and days and days before. I think that's one process that's really going to help me out, making sure my body is hydrated for the amount of effort we're putting in and working out."

Mathews has had some sort of injury every year since his sophomore year at Fresno State. Among other injuries, he's had three concussions, an MCL injury, a broken hand and a hamstring strain. He even broke his left and right clavicle in the same season. Last year's sprained MCL in his right knee and sprained right ankle limited him to only six games for San Diego.

Mathews has played a full NFL year only once, in 2013. Even during that year, he suffered a concussion and aggravated a hamstring injury, but he didn't miss any time. And one look at his numbers shows why the Eagles thought he might be an adequate replacement to McCoy.

Mathews rushed 285 times for 1,255 yards and six touchdowns. He also added 26 catches for 189 yards and another score. A healthy Mathews, even backing up Murray, is more than capable of being productive.

The Eagles list Mathews at 6 feet tall and 220 pounds, but Mathews said he's now at 230 pounds and feels strong, fast and quick.

"It's not about me trying to stay healthy," Mathews said. "It's all part of the luck. I've had some bad luck with the broken collarbones in the same year, the knee thing, the ankles and stuff. I think being in this system and everything that they're helping me out and doing is just really going to help my longevity in this offense."

Murray said after practice yesterday that there were a lot of similarities between himself and Mathews. Mathews agreed and said the physical aspect between the two when they run is a big similarity. That physical aspect, some say, is a big reason why McCoy is no longer in town.

"Ryan's been a really good addition to us," Kelly said. "[He's a] big, physical running back. I don't think you really know actually how big he is until you actually pull up next to him . . . He's explosive. When he sees a hole, he can change gears and accelerate through it. We're using him a little bit on kickoff return, I think because of taking advantage of that speed. There's not a lot of guys that have that speed to go along with that size.

"It'll be a lot different, too, with the pads on. I think he's one of those guys that, with the pads on, will become even bigger, because he's going to be a really tough guy to tackle."

Tougher than picking apart an uncooked filet? Maybe.