The Merseyside giants are unbeaten in all competitions this season and are going to Old Trafford with Mohamed Salah playing at his peak.
Manchester United have only earned a point from their last three league games and were in a gruelling 3-2 victory over Atalanta in the Champions League on Wednesday night.
Liverpool also had to work hard to beat Atletico Madrid, but they have had 24 hours more to rest, recuperate and prepare for the big game at Old Trafford on Sunday.
Thompson conceded that Ole Gunnar Solskjaer would have preferred it the other way round but feels come Sunday, the extra 24 hours or Liverpool’s form goes out of the window.
He insisted that Liverpool have to be on their guard regardless of Manchester United’s form as he believes the old enemy will bring their best to the table on Sunday.
Thompson said on LFC TV when asked if the extra 24 hours is an advantage for Liverpool: “Klopp and Ole Gunnar Solskjaer will say that it does make a difference.
“Ole would have liked it the other way round and so you are getting that 24 hours but come Sunday in such a game, I don’t think it will have anything to do.
“I know Manchester United have had their problems, but they are going to be at it on Sunday.
“You can say things, people are betting in what way it goes, but this just goes out of the window.
“This is the biggest game in world football and we just have to be ready for it, particularly in the first 20 minutes.”
Liverpool beat Manchester United at Old Trafford towards the end of last season in their remarkable winning run that saw them clinch fourth position in the league table.
