He doesn't duck, he shrugs his shoulders in an attempt to break the tackle.
I remember earlier in the season Lewis deliberately ducked and the media were all over it, and come on... watch Puopolo for christ sake.
Learn the game asswipe...he drops his knees as soon as he is about to be tackled...a technique mastered by the selwood sisters and the Eagles, resulting in a massive disproportion of free kicks for in comparison to the rest of the comp for the mentioned parties