Can you play a unit to your occupied battlefield during a showdown?

Ruling: Yes, you can play units to any location you control, including your occupied battlefield during a showdown. However, you can only play a unit during showdown if an effect specifically allows it (like Nocturne, Chompers, or Shen).

Sequence:

• You must control the battlefield (having a defending unit means you control it)
• An effect must allow you to play the unit during showdown
• The newly played unit participates in the showdown and contributes damage

Nuances:

• You control your base and any battlefield where you have a defending unit
• Not all units can be played during showdown - only those with effects that specifically allow it