Chris Polk knew what to expect when Chip Kelly left the University of Oregon to coach the Eagles last winter. Polk had played at the University of Washington a Pac-12 rival of the Ducks. He saw Kelly’s fast-paced offense first hand. So Polk knew he had to get in shape and get faster. He lost 15 pounds getting down to 215 and came into the Eagles’ training camp ready to compete for one of the backup running back spots. “It was very hard because I love food and I love to eat” Polk said. “But you’ve got to stay disciplined. It’s like a car. If you have a nice car you’re going to put 91 (octane fuel) in it. You’re not going to put unleaded in it. ... This year with different schemes seeing how many plays we’re running how many backs we have in this uptempo offense you have to be fit and be in really good shape.” So far Polk an undrafted free agent in 2012 has impressed the coaches with his speed and power running. He will need both this season. Polk is coming off a disappointing rookie year in which he didn’t get a carry and missed the final eight games because of turf toe. The Eagles also signed former Dallas Cowboys running back Felix Jones in May mainly to compete with Polk for the third running back spot.