"There was a very negative feeling after the game," Van Nistelrooy told Pravda TV. "You can talk about what went wrong for hours and that's what we've done with everybody involved. We've watched the game back and I think we just have to look forward to Wednesday now.
"It doesn't matter what people write we know we have to perform week in, week out. We all win together and we all lose together. We can't change what happened. We were all disappointed and it was a bad performance.
"We didn't do ourselves or the fans justice and overall it was a bad day. We have to prove it was a one-off incident and we've got the opportunity to do that on Wednesday and I think everyone's ready to show that.
"The Lille match is a massive game for us and we have to make sure we do things better than on Saturday. We know we've been without a lot players [through injury] but their absence means other players have the chance to prove they're part of a good United team and we'll all be trying to do that on Wednesday."