Ruling Defender

[Inigo Montoya]

I attach Defender to my Zekrom and attack with Bolt Strike, thus doing 20 damage to myself instead of 40 because Defender reduces self recoil in the same manner that PlusPower adds to it. The question is when I would discard the card. Would I discard at the end of my opponent's turn, as the card implies, or do I discard it after I hit myself with the recoil?

 

[DNA]

The card text says "Discard this card at the end of your opponent's next turn."
It does NOT say "Discard this card when the Pokemon this card is attached to takes damage."

Zekrom keeps the Defender for 1 full turn.