Liverpool are six points clear at the top of the Premier League table -- and are hot favourites to land a 20th English top-flight crown, which would pull them level with record-holders United.
United, by contrast, are 14th in the table after five defeats in their past six league games under new manager Ruben Amorim.
But Slot, also in his first campaign in England, is adamant he will not take his opponents lightly at Anfield, when asked if he might rest players at Friday's pre-match press conference.
"No, of course I'm not going to plan to rest any player because it's a big game and I think it's for me I said it before the first fixture (a 3-0 win at Old Trafford) and I can say it one more time, that they have much better players in my opinion than maybe the league table shows at the moment.
"I think it's going to take a while maybe for Ruben Amorim to bring this out of the players... but they will definitely go up and they are much, much, much better than the league table shows at the moment."
The Dutchman said he had sympathy with his rival in the Old Trafford hot seat, who joined United from Portuguese champions Sporting Lisbon in November.
"I think every manager sympathises with every other manager, because we all know how much pressure this job brings," said Slot.
"That's not different for him than for me, or for any other manager that works in the Premier League, or somewhere else around the world."
Slot was asked whether he could categorically state that Liverpool would not let Trent Alexander-Arnold leave in the January transfer window, with the defender heavily linked with a move to Real Madrid.
Alexander-Arnold, Mohamed Salah and captain Virgil van Dijk are all out of contract at the end of the season and can now talk to foreign clubs.
Slot said Alexander-Arnold was "fully committed" to Liverpool and would be playing on Sunday.
"Hopefully he brings the same performances as he brought in for the last half-year, because I think everybody saw how great a first half of the season he had, how much he is here, how much he wants to win here," said Slot."
