"We were talking in training about improving, showing character. We want a reaction from them and hopefully we'll see this," said Benitez.
"We can talk and talk about the gap to United but we have to get three points against Sunderland and then see what happens with them.
"We had chances on Saturday but after the first goal we were more nervous and anxious. After the second we started making more mistakes and it wasn't good enough.
"I was really disappointed and the players were also. But in training in the days after you cannot change what's happened - you just have to concentrate on Sunderland.
"We have to improve and show character to try to get the three points. Everyone knows how important the game is."
