It's likely that Hernandez is still feeling the effects of a high ankle sprain initially suffered during week two, and could have very well experienced a setback in his recovery last weekend against the Jets.
While his presence will be sorely missed, you have to commend the coaching staff for erring on the side of caution on this one. With a bye week on the horizon, this will allot two weeks for Hernandez to fully rest his ankle in time for the second half of the season and the playoff push.
TEs Michael Hoomanawanui and Daniels Fells—assumed to both be healthy as they have managed to escape this week's injury report—will likely see an increase in snaps. TE Visanthe Shiancoe has been activated off the freshly modified injured reserve, but he will be unable to see the field until after week eight as per the new rules.