Slot benched Salah for Sunday's breakthrough win at West Ham and Nicol says the same should happen tonight.
He said on ESPN: "He has to (leave him on the bench). He has to. Absolutely (they're better without him).
"You need to start from the back, you need the base to be right, to be solid and you need to stop giving goals away. You can't expect to score three or four goals every week to win a game.
"If he goes back (into the side) and breaks that shape up... at least they were solid defensively, because of Szoboszlai.
"Okay, he wasn't standing wide the way Mo does and just stands there and waits for the ball. He's getting involved, he's getting back inside, he's helping his full-back.
"The whole shape defensively was miles better. They're not going to get better if they just all of a sudden go back to what they were doing and teams start streaming through them again.
"You've got to look after the base, the solid structure that they had. Yes, it's against West Ham, but it was a solid structure.
"There was no real drama, no running all over the place, no holes. That's what you've got to go from.
"If he (Slot) changes it and brings Mo Salah back against Sunderland, to me that's a big mistake."