Brighton will be without defender Solly March for up to a month after he had groin surgery.
Solly, who missed Saturday's defeat at Liverpool due to the problem, went under the knife on Monday and will miss the Christmas period.
"He has had some surgery at the start of the week," boss Graham Potter said in his pre-match press conference, as reported by Brighton and Hove Independent.
"So he will be (out for) three to four weeks. It was in his groin area and we just needed a bit of work there. It is disappointing for him and for us of course.
"He had pain and the way he plays, he is a sprinter. It is better just to get it cleared up, it was the best option for him.
"It has happened over a period of weeks. It came to a head after the Leicester game. He took a free-kick and just aggravated it a bit more."
The Seagulls head to the Emirates on Thursday night in what will be interim head coach Freddie Ljungberg's first home game in charge of Arsenal.
Potter's side put on a good show at Anfield at the weekend, losing 2-1, and he wants more of the same in north London.
"Arsenal are a top club with good players and they are looking for a reaction," he said.
"Freddie has had one game at Norwich and he'll be looking at new things. We need to make sure we are at the level we need to be to get something from the match."
"It was disappointing to not come away with anything against Liverpool, but I was proud of what we did.
"If you can't win then you need to take something from the performance and I think we did that."
On his squad news, he added: "Bernardo is in the squad training. Everyone apart from Solly March and Jose Izquierdo is available.
"With a busy period coming up it's my job to pick the right combination for the team to win matches."
