If Teemo, Strategist is played from hidden as a reaction to an opponent's attack, does his 'when it defends or is played from hidden' ability trigger twice?

Ruling: Teemo, Strategist only triggers once when played from hidden during an opponent's attack. He was errata'd so that his defend trigger happens when a unit is played to an already ongoing combat.

Nuances:

• When a unit is moved into an ongoing combat, it triggers "when I attack/defend" effects
• A unit swapped in by Tideturner during an opponent's attack would trigger its "when it defends" ability as it is now defending