Pardew admitted the patched-up side he fielded at Amex Stadium was inadequate but stressed the club must concentrate on relieving their precarious position in the Barclays Premier League.
"We need to make sure we are a Premier League team next season. Our team today is a shadow of the team we can put out," he said.
"We know we need to get some bigger players who can handle the situation of carrying a Newcastle jersey, whether that's a signing or getting a player back from injury.
"It's important to spend during this month. I'd like to see another player come in through the door to join Mathieu Debuchy in the next week or so."
He added: "There are young players who have given everything there, their maximum performance. But unfortunately they shouldn't be playing for Newcastle in the third round, they should be in our development team."
Papiss Cisse and Fabricio Coloccini were missing with respective thigh and hamstring injuries, though both are expected to return against Norwich on Saturday. The influential Hatem Ben Arfa, Yohan Cabaye and Steven Taylor are out until next month, Cheick Tiote has been lost to the African Nations Cup and Demba Ba was sold to Chelsea on Friday.
It is the second successive year Brighton have dumped Newcastle out of the FA Cup with goals from Andrea Orlandi and Will Hoskins humbling their Premier League opponents.
"We had a great opportunity because of the players that were missing to beat a Premier League team. What a team you could make up of the players they had missing," manager Gus Poyet said.
"But it was more up to us than the opposition. We deserve it because of the way we played. We were the better team."