Chris Polk could be losing ground in the competition to make the Eagles' roster as a reserve running back after missing the last two weeks of practice with a torn hamstring.
Polk, 24, has not played in either of the Eagles' preseason games. Running backs Matthew Tucker and Henry Josey are other backs competing for a roster spot behind LeSean McCoy and Darren Sproles.
Kelly addressed the media Tuesday:
"It's a big factor," Kelly said of Polk missing time, according to NJ.com. "You gotta be able to play. It's tough for us to say, we know what you can do, but you also have to go out on the field and show it.'
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Polk, 24, rushed for 98 yards and three touchdowns on 11 carries in 15 games with the Eagles last season. He went undrafted out of Washington in 2012.
Polk, who has been running away from regular team drills at practice, according to reports, said he fears re-aggravating the injury if he returns prematurely.
The Eagles' next preseason game is Thursday against the Pittsburgh Steelers.
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