When is the hydra considered a player with the "Face the Hydra" deck?
is the hydra considered a player?


Yes, there is a player as normal.


  For instance, I have a creature that gets +1/+1 counters each time it deals damage to a player. Would that ever be triggered since you attack its heads directly?


Creatures attacking heads directly deal damages to the heads they attack.

Creatures not attacking heads directly attack the player as normal. However, damage that would be dealt to the player is dealt to a head instead. As such, you never actually deal any damage to the player.

In both cases, the attackers deal damage to the heads. The heads are creatures, not players. The ability in question would not trigger.


  What if that creature was unblockable?


It doesn't make any difference.