Perhaps it's your expectations then, that are a bit unrealistic? Pirlo is one of our best performers. I don't think we would've been in the top 3, even, without this player.
I thought the problem was more that the chance was really there as a header and Pirlo doesn't like to head the ball.
That made the option of going down easily more attractive.
Anyway, technically it should have been a penalty, but it would have been pretty soft and I don't think the ref can be blame for not seeing the contact.