Late Tackles

Watching the Liverpool v Stoke game and the bit where Walters got through and shot across the face of goal, it got me thinking about late tackles. Most places on the pitch, if a player has already played the ball and then gets hit late by an opponent it's a free kick and very likely a yellow card. Yet somehow, if someone shoots and then gets hit late it is ignored. It's a licence for defenders to have a free shot at a forward with no punishment. Logically there's no real reason why the Sakho challenge on Walters shouldn't have resulted in a penalty.

I must be bored!