Defending players question

[Nonex]

I know that Planeswalkers being attacked are defending Planeswalkers, but are their controllers considered defending players if no one is attacking them?

[luma]

Yes, they are.

506.2. During the combat phase, the active player is the attacking player; creatures that player controls may attack. During the combat phase of a two-player game, the nonactive player is the defending player; that player and planeswalkers he or she controls may be attacked.

Also, if an attacking creature's ability refers to the "defending player", it means the player the creature is attacking, or the controller of the planeswalker that creature is attacking.

508.5. If an ability of an attacking creature refers to a defending player, or a spell or ability refers to both an attacking creature and a defending player, then unless otherwise specified, the defending player it's referring to is the player that creature was attacking at the time it became an attacking creature that combat, or the controller of the planeswalker that creature was attacking at the time it became an attacking creature that combat.