The Panthers find themselves suddenly very thin at safety and in need of more than just bodies.
While Whitner would be a nice addition to the secondary it seems unlikely the Panthers would pay starter money to a back-up player. Sure he could start if called upon but the starters are set and healthy at the moment.
Coleman and Boston are locked in as starters. Sure, Whitner went to three straight Pro Bowls starting in 2012, but his visit is all about depth. Whitner would add another veteran voice to a secondary that doesn't have many of those past Coleman.