Arsenal suffered a setback on Wednesday when they announced Dutch defender Jurrien Timber would be sidelined with a major knee injury.
The 22-year-old damaged the anterior cruciate ligament in his right knee during the Gunners' 2-1 win at home to Nottingham Forest in their opening match of the new Premier League season last weekend.
A statement on Arsenal's website said: "Jurrien will undergo surgery in the coming days and will be out of action for a period of time.
"The support and expertise from our medical team and everyone at the club will now be focussed on Jurrien's rehabilitation programme, to ensure he recovers well and is back playing as soon as possible."
Timber only joined Arsenal, bidding to go one better than last season's second place in the Premier League, in July in an initial 40-million-euro ($45 million) move from Dutch giants Ajax.
He won two Eredivisie titles in 121 appearances for Ajax and was a member of the Netherlands squad that reached the quarter-finals of last year's World Cup.
He can operate at both centre-back and right-back and it had been hoped he would bring added depth to an Arsenal defence that struggled to cope with injuries to William Saliba and Takehiro Tomiyasu towards the end of last season.
Timber's arrival at the Emirates Stadium came as a part of a pre-season spending spree that saw Declan Rice and Kai Havertz join the club, with the trio's combined transfer fees totalling in excess of £200 million ($254 million).
Arsenal, however, may now have to go into the transfer window again to get cover for Timber, with Mikel Arteta's side looking to overhaul treble-winners Manchester City as Premier League champions.
The Gunners' next match is away to Crystal Palace on Monday.
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