Slot’s side are in danger of slipping out of the top four with fifth placed Aston Villa set to face relegation threated Tottenham in the late kick-off.
Liverpool managed to come back from 2-0 down at Old Trafford to make it 2-2, but Kobbie Mainoo’s 77th minute goal secured the win for Man United.
Speaking to reporters after the game, under pressure Slot insisted that his side are too far off being back to their best.
"We weren't able to control their strengths. We were aware of them - set-pieces and counter-attack. You have to know where to lose the ball if you play against United,” he said.
“They are really strong when they play into the middle. They have so many fast players, Bruno Fernandes to hurt you in transition and that's exactly what happened with the second goal.
“That is what happens. We were 2-0 down, came back in the second-half to 2-2 and then we shut off and immediately conceded the goal."
On things to work on for next season: "The margins are not so big on us being able to win a game like this, I know what we can improve on and we are already working hard on this.
“The same issues keep coming back which is not a huge surprise as you don't have long to fix it during the season.
“Tactically you can change certain things but for me it is clear we have to improve and we will."