Hernandez sprained his MCL in Week 2 against the Chargers and missed last Sunday's 34-31 loss at Buffalo.
The second-year pro has 165 yards receiving and two touchdowns on 14 receptions so far this season.
Vollmer (back) has appeared in just one game this season.
Defensive tackle Albert Haynesworth did not practice Friday due to a back injury. His status for Sunday is questionable.
Others listed as questionable include cornerbacks Kyle Arrington, Leigh Bodden and Ras-I Dowling, safety Patrick Chung, defensive lineman Shaun Ellis, linebacker Gary Guyton, wide receiver Taylor Price and offensive lineman Ryan Wendell.