As a point of context here around the laws designed to, take care of player safety, then why is it that a ball carrier, as in this instance (Esterhuizen) can lead with his shoulder, and a tackler cannot? In my opinion, both players lead with shoulders forward, and both came out a little tinged. Fair contest might be the view of many neutrals. To the letter of the law, it looked a pen to me. Dangerous by Farrell.
I've seen loads of instances where a would be tackler has simply gone in too high to a big player, and been knocked back on his arse, indeed out cold, coming into contact with the ball carriers leading shoulder. The ball carrier has never been penalized, to my knowledge.
Still thought it was a pen, but to suggest laws can stop players getting hurt in a game of rugby is rich at times.
Apologies for my previous comment suggesting Esterhuizen a forward. He'd be a forward in my team at nearly 2 meters and 220 lbs. he still outgunned Farrell, who stopped him in his tracks. Great collision. One of the best you will see. And legal apparently. Everyone will be at it now.