Spikes played significant snaps against the Bucs, I think it depends on the opponent, whether the Patriots want to dedicate a defender specifically to stopping the run or blitzing if the offense goes pass. Spikes can be very effective.
As for Ryan, he was not seen until the second half and a lead was built, most likely trying to get him some experience...at least until Dennard went out with an injury.
I agree that Spikes playing for the Patriots next season is up in the air, but I still love his physical play.