Will contract keep Meachem on roster?

Robert Meachem appears to be in a terrific situation. His roster spot seems secure, since his $5 million salary is guaranteed for 2013. No. 1 San Diego Chargers WR Danario Alexander is out of the season, new No. 1 WR Vincent Brown has a lengthy injury history, and the Chargers lack depth in their WR corps. So why is he still desperately clinging to his spot on the roster? He looked downright awful in their exhibition opener.