Alan Pardew reacted to yesterday's FA Cup loss to Brighton by declaring his club must buy in the transfer window to address the injury crisis that has struck Newcastle United.

Pardew admitted the patched-up side he fielded at Amex Stadium was inadequate but stressed the team must concentrate on relieving their precarious position in the Barclays Premier League.

Papiss Cisse and Fabricio Coloccini were missing with respective thigh and hamstring injuries, although both are expected to return away to Norwich City on Saturday. Hatem Ben Arfa, Yohan Cabaye and Steven Taylor are out until next month, Cheick Tiote has been lost to the Africa Cup of Nations and Demba Ba was on Friday sold to Chelsea. Newcastle are two points above the relegation zone and Pardew warned the club must act if they are to remain in the top flight.

"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."

Brighton repeated last season's FA Cup heroics by beating Pardew's side, with Andrea Orlandi supplying an outstanding opener.

The first-half strike came from Wayne Bridge's willingness to chase a seemingly lost cause, but it was Orlandi's exquisite touch, turn and shot that stole the show. The Spanish playmaker was applauded by both sets of fans as he departed with half an hour to go.

The second goal was scored by substitute Will Hoskins after David Lopez's defence-splitting pass, and the npower Championship play-off hopefuls completed a comfortable win.

Apart from their FA Cup failure at the first hurdle – last year they lost to Brighton in the fourth round – Newcastle were further frustrated by captain Shola Ameobi's second-half sending-off. Ameobi was deeply unlucky to receive the second yellow from referee Lee Probert and will miss Saturday's match against Norwich, leaving Pardew short of striking options with Cisse injured and Ba gone.

The victory could be just the tonic Brighton need to revive the top-six league aspirations that have been dented in recent weeks, while history points to a profitable cup run: they reached the final 30 years ago having beaten Newcastle in the third round, and last year got as far as the fifth round of the competition before being beaten 6-1 by Liverpool.

From the start it was clear that the Seagulls sensed an upset was on the cards, Dean Hammond firing a shot over the crossbar and, apart from a Gael Bigirimana strike which tested Brighton goalkeeper Casper Ankergren, the half belonged to the home side – who capped their dominance with Orlandi's superb goal.

Newcastle replaced Mehdi Abeid and James Perch with Paul Dummett and Nile Ranger for the second half but Brighton still looked comfortable and the dismissal of Ameobi for his second yellow card left them a man down for the last half-hour.

The visitors still showed flashes of determination, however, with Liam Bridcutt hurling himself in front of a shot by Sylvain Marveaux and Ranger heading over the bar.

Newcastle pressed hard for an equaliser but the second goal was delivered by Brighton, Lopez releasing Hoskins one on one with goalkeeper Rob Elliot for the substitute to put the tie beyond doubt.