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O'Riley was forced off ten minutes into his Brighton debut against Crawley after his big-money move from Celtic, after being on the receiving end of a strong challenge.

Hurzeler confirmed that the Danish international will be on the sidelines for a while, and hopes the whole club can rally round him during his recovery.

"It's a bad injury, he needs ankle surgery and I can't say how long he's out," he said. "We will support him and try to get him back fast on the pitch.

"He's a good character, and is a really positive guy. It's really important to stay mentally strong and I am certain he will come back stronger from this."

O'Riley was the second-highest goalscorer in the Scottish Premiership last season with 18 goals, while he also provided the most assists in the league with 13.

The 31 year-old manager also praised the vision of Tony Bloom, who has backed Hurzeler with the club's most expensive ever outlay this summer.

Along with O'Riley, the club has spent almost £200million on the likes of O'Riley, Mats Wieffer, Yankuba Minteh, Ferdi Kadioglu and Georginio Rutter.

"I feel grateful and thankful for [chairman] Tony [Bloom] because it shows the ambition of the club and that we want to build on a foundation and make improvements," said Hurzeler, who is just the fourth Brighton boss to win his opening two league games in charge.

"I'm a very ambitious guy and hope that we can achieve something big together."

Brighton travels to Arsenal for its third match of the Premier League season.

The Seagulls have won three of their seven Premier League away games against Arsenal.