Henderson admits Liverpool must improve if they are to get the better of United.
"The onus is on us to raise our game because we haven't been at our best lately," said the skipper in his programme notes. "We don't need anyone to tell us that.
"As a player you know when you have rhythm and you know when you are playing well. There haven't been too many occasions in the last few weeks when we have ticked both of those boxes.
"It's been a bit of a slog, there's no question about that.
"But it shouldn't be forgotten that we have put ourselves there or thereabouts in terms of league placing and that bodes well given we are fully aware that there is a fair bit of improvement still to come.
"This is a game in which you only get to display your quality if you have the work-rate and commitment required to compete.
"Anyone who has ever watched this game knows exactly what to expect. The points will not be gifted. If we want them, we will have to earn them."