If my opponent initiates a showdown on an empty battlefield, can I use Ride the Wind on Overzealous Fan and use his ability to push the attacking unit back?

Ruling: Yes, you can use Ride the Wind to move Overzealous Fan to the battlefield during the showdown, and his "When I defend" ability will trigger and allow you to push the attacking unit back.

Sequence:

• Opponent moves a unit to an empty battlefield, beginning a showdown
• During an Open state, you play Ride the Wind as an action
• Ride the Wind resolves, moving Overzealous Fan to the battlefield
• During the cleanup phase following Ride the Wind's resolution, Overzealous Fan gains the Defender designation
• Overzealous Fan's "When I defend" ability triggers and is placed on the chain as a pending item
• Players may respond to the trigger before it resolves

Nuances:

• Units that enter the battlefield after a showdown has begun gain the Defender designation during the cleanup phase following the action that caused them to become present, not immediately
• Defend triggers activate when a unit gains the Defender designation for the first time during combat, even if that designation is gained mid-showdown