Why didn't that big fat bacon faced bribe taking retard make a fucking change if his player was so badly injured?
Because, bar a few exceptions, all managers are insanely biased and one-eyed when it comes to talking about their own team and refereeing decisions. They're shameless about it. Pochettino said the push on Sterling wasn't a pen, and it's the most blatant pen you'll ever see anywhere. Klopp was bemoaning bad luck for conceding 3 appalling goals to a fairly ordinary team, Wenger and Mourinho almost never accept or concede anything, no matter how ludicrous the point and I dare say Koeman has done it, or will do it at some point.
It's pretty lame really. I think people would have a lot of respect for managers that just said 'nah, it was a pen in fairness' or 'nevermind luck, we defended like shite' and it would probably decrease the pressure on referees and enhance their performance as a result.