Jackie McNamara's men could be without six first-team players through injury and suspension at Tannadice.
Suspended midfielders Willo Flood and John Rankin join long-term absentees Gavin Gunning and Johnny Russell on the sidelines while Jon Daly and Brian McLean are both fitness doubts.
The Dark Blues are still searching for their first derby triumph this season after losing three on the bounce against their biggest rivals.
But Brown, who is set to hand former Everton goalkeeper Steve Simonsen a debut in place of the injured Rab Douglas, does not believe United will be a shadow of themselves come Sunday.
Brown said: "We won't be thinking like that. We all know how these things work in football.
"It will be 11 versus 11 at the end of the day.
"No matter who they put out they will be eager to impress the manager and keep their place so they have an opportunity in that respect.
"The players they could have out have been standing fixtures but it gives other guys an opportunity to come in and stay in the team.
"So it will create other problems that I will have to look at.
"They will be hungry players coming in and we will have to be determined to match that.
"It's their home game but it's a big one for us as we try to stay up.
"United have turned us over in the league games this season so we want that to change.
"We are determined to get to the split with the gap down to single figures.
"If we do that, that will put pressure on the teams above us and ask a question or two of them."
Brown has challenged his players to forget about past results and focus fully on changing that losing trend in Sunday's televised match.
He said: "This is a clean slate. It doesn't matter what has gone on before.
"That is all in the past as far as we're concerned.
"It's only what happens in the future that matters and we're going to be very positive on Sunday."