Brighton boss Fabian Hurzeler says FA Cup opponents Newcastle can not replace “special” Alexander Isak should the Swedish striker miss their fifth-round tie through injury. The superstar striker is unlikely to be fit for the clash but the Seagulls chief admits he won't 'gamble' on the player missing the game.

Isak has scored 21 goals this season but sat out the Premier League defeat at Liverpool on Wednesday with a groin issue. Newcastle boss Eddie Howe remains uncertain over Isak’s fitness for Sunday’s cup clash at St James’ Park.

“He is a special player – a player who can make the difference,” Hurzeler said at his pre-match press conference. “You can’t replace a player like this because not every team has two, three or four players of this quality. Therefore it is a different game if he doesn’t play.

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“The thing now is we don’t know, so we really have to prepare that Isak will start. To prepare for his actions, his behaviour, how we want to defend this together as a group. So you can’t gamble and say he won’t play.

“I’m sure they will try to do everything to make him fit for the game and we have to be ready for that.”

Isak's importance to Newcastle's season has become more evident over recent weeks. While he has 21 goals this season, the next top scorer is Anthony Gordon with just nine, while Jacob Murphy has six. United's reliance on the Swede shows just why they will resist any bids from Liverpool or Arsenal for the striker's services this summer.

Newcastle have slapped a £150m price tag on Isak's head and also said they won't look to cash in even if they don't make the Champions League at the end of the season.

Brighton, meanwhile, have bounced back from their 7-0 humiliation at Nottingham Forest by winning four consecutive games. Tuesday’s home victory against Bournemouth lifted them to eighth in the Premier League, just three points off a potential Champions League spot.

Hurzeler said: “For sure when you win four games in a row there’s a lot of positivity in the building and a great atmosphere.

“In general I always try to say that we want to stay stable and particular in our behaviour and work ethic, because you can’t get too euphoric when you have a great run or too depressed when you don’t get the results you need.

“At the moment we have the results that we want, and it’s important to understand now why the results came and why we are in this situation. We have to continue these things so don’t do less, invest even more to keep the momentum. This will be our job now and then I’m sure we can continue this run.”

Skipper Lewis Dunk is again likely to be absent with a rib injury, but fellow defender Eiran Cashin will be available after missing out on the squad last time out. Cashin has yet to make his debut since joining from Derby in January.