Whether it's Michael Vick or Nick Foles or someone else at quarterback, LeSean McCoy and Bryce Brown will be carrying a great deal of the load on offense. In Kelly's up-tempo offense, even two running backs won't likely be enough.
"You're running so much, it's like a freaking track meet," McCoy said Thursday after the Eagles' final practice of a three-day minicamp. "It's like a relay. You need extra guys."
At Oregon, the quarterback normally helped out on the ground. There were seasons when Kelly didn't have a "mobile" quarterback. But that didn't mean he ran the ball less. He just handed to ball off more to his tailbacks.
If Vick or Dennis Dixon or a rookie quarterback with fast legs wins the job, then the offense will have its share of read-option plays. If the immobile Foles wins it, then it won't.
But either way, there will be plenty for McCoy, Brown, Chris Polk, or someone else to share. Oregon running backs rushed 39.2 times a game last season. The Eagles, on the other hand, averaged 20.9 carries.
Again, there's little chance Kelly runs the ball as much as he did at Oregon. But even if the scales are more balanced, the number of plays in his up-tempo scheme will increase the carries.
"I think any back, no matter how great of shape he's in, he's going to need some extra help," McCoy said. "I know that. Bryce is good enough. He can play."
When McCoy was sidelined for four games last season with a concussion, Brown exploded as the starter. He rushed for 347 yards and four touchdowns in the first two games but tailed off in the next two, managing only 40 yards on 28 totes.
And as well as he ran in his first two starts as a rookie, Brown lost three fumbles. He said Thursday that he worked on ball security during the offseason by carrying around a weighted football.
Despite the turnover problem, Brown's upside was encouraging. And with Kelly in charge, the options with McCoy and Brown in the backfield seem endless.
McCoy said that the Eagles have practiced more passing than running plays thus far, which is typical during noncontact sessions. But the emphasis has been more on the speed of Kelly's offense than on any particular plays.
"I think we'll be in the best shape in the league, for sure," McCoy said. "There's never a time where we're breaking.
"In this offense, we're shifting, moving. As soon as you get tackled, there's no celebrations after the play. . . . I think . . . by the second or third quarter, defenses will be tired."
But will the Eagles' offensive line be as tired? Kelly had the luxury of 18-to-22-year-olds at Oregon. Three of his projected starting linemen - tackles Jason Peters and Todd Herremans and guard Evan Mathis - are over 30.
"I don't really see too much of a difference," Herremans said.
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