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Charlie Neibergall, Associated Press
Iowa running back Jordan Canzeri is helped off the field on a cart after Iowa's annual NCAA college football spring scrimmage, Saturday, April 14, 2012, in Iowa City, Iowa. Canzeri was injured during a practice earlier this spring.

IOWA CITY, Iowa — Iowa has long been known for its punishing running attack. But the Hawkeyes will wrap up spring ball next week with serious questions to answer about their running back situation.

Iowa is down to a pair of unproven sophomores, Damon Bullock and De'Andre Johnson, after Marcus Coker's departure and Jordan Canzeri's knee injury. True freshmen Greg Garmon and Barkley Hill join the team in August.

Iowa coach Kirk Ferentz says Bullock and Johnson have made consistent improvement this spring. He also says they've told Garmon and Hill to do everything they can to be ready to play by the end of the summer.