PHILADELPHIA (CBS) – The Eagles will have plenty of problems with what the see on the field itself on Sunday in Denver. The Eagles biggest weakness is their secondary, and the Broncos biggest strength is their passing offense. It’s a recipe for more than a couple of problems.

But they’ll also be battling something that isn’t quite on the field, but in the air; the altitude in Denver. It’s a well known issue, players not used to playing in the altitude in the mile-high city have more trouble keeping up with those who do. The Denver Nuggets used it to their advantage last year, pushing the pace of the game en route to a 38-3 record at home, the best in the NBA.

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Chip Kelly acknowledges it’s something the Eagles will have to deal with, but maybe not in the way you’d think. It will be something in their heads, not in their lungs.

“I think a lot of it is mental and it’s not as big a deal as people make it out to be,” Kelly said on Tuesday. “I think what makes a difference when you play at altitude is who you play against. We played against the University of Colorado a couple years ago, it wasn’t a big deal. You play against the Broncos, it’s a big deal. It’s an anaerobic sport. It doesn’t affect you the way you think. We’re not going there to run a marathon.”

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One advantage the Eagles will have is rest. The Broncos will play the game on a short week of rest after their Monday night over the Raiders. The Eagles on the other hand, finally get a break in the schedule with 10 days in between Sunday’s game and their Thursday night loss against the Chiefs.

“I mean, that’s just the way the schedule laid itself out. We knew it going in. We had a plan going in what we were going to do. We knew they needed a little bit of a break because you were playing three games in 11 days. They were off over the weekend and on Monday, and back together today,” Kelly said. Peyton Manning thanked the sarcastically NFL after their Monday night game for giving the Eagles a rest advantage going into the game. Kelly was less than sympathetic. “When do we go play? We go play in a parking lot, we go play in a parking lot. We don’t care. We played three games in 11 days. We don’t control the schedule. We only carry about what we can control.”

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