Warrior Minotaur - passive ability prevents revenge and counter attacks.

Sentinel Werewolf - passive ability has small chance to counter attack.

I had this situation in the Arena just now, I had the warrior minotaur on my team, and the opposing team had the sentinel werewolf.

The werewolf was able to counter attack my team. My minotaur did not have any negative effects that would have disabled its passive ability.

So, how was the werewolf able to counter-attack, ignoring the minotaur's passive which prevents counter attacks ?