Darren Sproles has only one speed.

It's the same one that fueled the Eagles running back and return-man 89 yards for a touchdown on a punt return against the Jets Sunday. 

And it's a speed that Chip Kelly can't help but enjoy (and sometimes worry about) in his under-sized but under-rated utility back.

"There's one speed with Darren," Kelly said of the 32-year-old, 11-year pro. "Every time he catches a punt in practice he scores a touchdown. And in a game, every time he gets good blocking, he's going to score a touchdown."

Sproles added a second six points to the Eagles' point total Sunday in a one-yard touchdown dart after Jordan Matthews just failed to break the plane on an inside pass from Sam Bradford. And his two touchdowns were certainly the difference in the 24-17 decision in New York in Week 3.

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"I've never been around a guy who practices as consistently and as hard as Darren does every day," Kelly said. "In walkthroughs, we ask him to slow down and he doesn't. He goes full speed. If we have a walkthrough punt he's going to sprint 60 yards from it and score a touchdown.

Kelly says the contagiousness of Sproles' work-ethic is a great asset, but can also be dangerous. He recalls telling punter Donnie Jones to slow down in walkthroughs, as the punter was trying to chase down the speedster Sproles. Kelly was worried his punter would pull a hamstring.

"That's just the way he's built and the way he's wired," the coach continues. "What you see Sundays from Darren is what we see every day. It's an amazing thing to watch, I wish more players would emulate it."