http://www.bjpenn.com/conor-mcgregor-checks-leg-kick-breaks-mans-leg/
Not sure when this happened but if he can effectively check a leg kick, then that's good news for the pro McGregor side!
At the end you can kinda see the leg bend when he puts weight down! 
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Dan The Wolfman taught him this move at a secret 'dark arts' ceremony hosted by Steve Seagal.