at least grygera has played the past few seasons, zebina has played minimal games. Grygera can be back up for both full back roles and can play as a centre back if need be. Zebina can only play RB or CB.
anyway, if a club wants him, i say sell him...i woudlnt take the risk of putting hopes on him to play this season. he is injury prone and when playing at best isnt great anyway.