Manchester United boss Louis van Gaal says it's crucial they keep 11 players on the pitch tomorrow at Liverpool.

Van Gaal admits it's crucial to keep emotions in check.

"I shall always warn my players about red cards because it is always sharp. The referee can be also, in circumstances where the environment is sharp for him. But also the players - when there is a wrong decision, they have to control their emotions and that is not so easy.

"I talked about emotion also in our preparation before the Arsenal match [in the FA Cup], for example. It was still a red card [for Angel Di Maria] and I have to say Arsenal also deserved a red card but the referee was saving that player. You need also a little bit of luck."