There must be something in the water here in Iowa City that repels running backs that play for the Iowa Hawkeyes.

There's no other explanation.

How else do you explain why running backs keep getting in trouble or hurt or encounter some other personal issue and decide to leave the school? It's happened five times in the past few years, including most recently, Marcus Coker.

He was the promising and, by many accounts, bright starting running back from Maryland who was suspended from the team in December. Iowa announced on Tuesday the sophomore requested and was granted permission to transfer. 

There is still no public explanation for what happened. The Iowa City Press-Citizen reported that Coker was a suspect in an October sexual assault case, but no arrest was made and the school refused to say whether that had a connection to his suspension.

Coker was only the latest young running back of whom great things were expected only to flame out early.

Remember Jewel Hampton? He showed flashes of brilliance as the backup to Shonn Greene, and was expected to be the featured back in 2010. Or, how about Brandon Wehger? He helped carry Iowa to a win in the Orange Bowl two years ago with other players injured. And, there's Adam Robinson, who was starter for most of last year, and freshman Mika'il McCall, who shined for about 30 minutes before getting injured in the first game this season.

Gone. Gone. Gone. Gone.

Iowa may need to put a disclaimer in their offer letters to running backs: If you come to Iowa don't drink the water; it's been known to make running backs want to leave.