Slot accepts this clash will be his team's biggest test so far this season.
He said at today's media conference: "If you look at the league table, it is. I think Manchester United is a very good team, a top club in England that has spent a lot of money to even make the team better again.
"Same for Chelsea in this season. Chelsea does really well. If you look at the league table then they are the ones that might be our toughest opponent. But it's not always about the league table. Sometimes it's about the form of the day, it's about their game plan. We had some difficulty with Wolves as well, who are bottom of the league, I think. But it is a challenge, that's for sure.
"If you want to achieve something in this season, you need to be defensively really stable. We've been that until now. Again, the fixture list we have to take into account as well. And now we face even better players because I agree with you that Chelsea, like Man United, has a lot, a lot, a lot of great individuals who we have to try to manage, to control.
"That's not what one player does, that's what we have to do as a team. But we must not forget to create our own chances as well, because if you want to win, you need to score as well. Fortunately and the good thing for us is that we have players that can score goals. Looking forward to a very interesting game on Sunday."