Steve McClaren's side hold a 2-1 lead in the sides' Championship play-off semi-final tie after a hard-fought triumph at the Amex Stadium on Thursday.
Jesse Lingard put Brighton ahead in the first half, only for Chris Martin to level from the penalty spot 11 minutes later.
Derby seized their advantage in fortuitous circumstances though, Martin's long-range effort striking the crossbar and bouncing in off the back of Brighton goalkeeper Tomasz Kuszczak.
McClaren may be confident coming into the game, with Derby having won nine of their last 11 games at Pride Park, but he remains wary of Oscar Garcia's side - who themselves have lost just one of their last eight on the road.
"We are satisfied with the result but we can be better and we will need to be better on Sunday because this tie is not over," the former England coach said.
"Brighton are a good team away from home. The first goal on Sunday? It's crucial.
"Brighton have nothing to lose. They can take risks - and we want them to, knowing that we can cause them problems on the counter-attack."
Awaiting either Derby or Brighton will be the winner of Wigan Athletic and QPR's tie.
The pair played out a 0-0 draw at the DW Stadium on Friday, putting the odds firmly in the favour of Harry Redknapp's side.
Friday's game will be Wigan's 62nd of a jam-packed season and just three wins from their last 11 Championship games hints that tiredness may be creeping in.
A further worry for Uwe Rosler may be QPR's excellent form at Loftus Road this term - QPR have lost just two league games in the league this season, against champions Leicester and Reading.
Regardless, the German believes that record only serves to heap more pressure on QPR - looking to bounce back to the Premier League at the first time of asking.
"The pressure's on QPR now," Rosler said. "At times I felt we could have been a little braver in terms of filling the box with more people, having the wing-backs a little bit higher up.
"We had two or three big chances and in games like that, when you play against top teams, there will be not many chances and you have to take them.
"They came here (to Wigan) to get a draw and they got that. I still count our chances as 50-50."
