From Charlotte.com:

After determining that Kalil would start at center next season, the
Panthers planned for Hartwig to compete at right guard. But Hartwig
prefers center, and Hurney said the team didn’t want to force him to
play out of his natural position.

"Certainly we were very happy
with what Justin did for us," Hurney said. "This was more of a case of
trying to do the right thing for the player at the right time."

It
also exemplifies the Panthers’ confidence in Kalil, a former Southern
Cal All-American who was rated the top center available in the 2007
draft.

Great news for Ryan.