Charles was a fourth-round pick in the 2012 NFL draft and was expected to be a compliment to former first-round tight end Jermaine Gresham so the Bengals could set themselves up with a Rob Gronkowski and Aaron Hernandez situation. However, the team's first-round selection of tight end Tyler Eifert in 2013 has ruled Charles out of that equation.
Suddenly it appeared Charles would fight for a roster spot with free agent signee Alex Smith and he was in risk of being cut before the Bengals even knew what they had.
The Bengals typically keep three tight ends, but if they move Charles to fullback, they could keep both him and Smith on the roster in 2013. Of course, this would mean they may not keep a traditional fullback like Chris Pressley or John Conner. The Bengals didn't have a fullback in 2010 but have had one since then. They also kept two fullbacks on the roster in 2008.
If the Bengals are hoping to keep both Charles and Smith on the roster while only keeping three tight ends, moving either Charles or Smith to fullback will likely be the best way to do so.