Brendan Rodgers' side ran out comfortable winners against their bitter rivals at Old Trafford, underlining their title credentials with what was a fifth successive league win.
However Henderson says Liverpool are already focusing on their next game, against Cardiff City on Saturday.
"It was a big win but it was just another game for us really," said the midfielder. "We went there trying to do the same thing, put on a good performance, get three points and thankfully we did that so we can move on to the next performance and hopefully win that.
"We knew it was a massive game but we have been brilliant of late and we felt as though we were capable of doing what we have been doing all season and have a really good chance of winning the game.
"We dominated from start to finish and I am very pleased in that respect, but we just move on to this week against Cardiff, that will be a difficult task as we are away from home so we need to prepare well for that."
Defender Jon Flanagan believes their rivals at the top of the Premier League will be "worried" as the season enters its final stages.
"I think they are going to be worried," said Flanagan.
"We put a marker down (at Old Trafford). I think we are ready to push on and keep going.
"We all believe but our priority was to finish in the top four at the start of the season. We are on track for that and anything else is a bonus.
"It's always good when you see other teams around us losing. We saw the Chelsea result (losing at Aston Villa on Saturday) but we just concentrate on ourselves.
"We are just taking it a game at a time and keeping our feet on the ground.
"Momentum is building though. The lads are really happy but we are taking it step by step and hopefully we can keep that going."