Arsenal’s new signing Jurrien Timber is set for a significant spell out of action after confirmation he has suffered a serious knee injury.

The Dutch international signed for the Gunners from Ajax for £40million this summer, and started both the Community Shield and Arsenal’s opening-day Premier League win over Nottingham Forest on Saturday.

But the 22-year-old was substituted early in the second half against Forest after sustaining a serious injury to his right knee. Scans confirmed on Wednesday that it is an anterior cruciate ligament injury.

Timber will now have knee surgery to try to correct the injury and give himself the best chance of a full recovery. The news of its severity is a major blow to manager Mikel Arteta as Arsenal bid to challenge Manchester City.

A statement from Arsenal on Wednesday read: “Further to detailed assessments with consultant specialists since Saturday, we can confirm that Jurrien has sustained an injury to his anterior cruciate ligament in his right knee.

“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.”

Oleksandr Zinchenko is expected to step up at left-back for the foreseeable future, while the injury may have knock-on effects for the club’s efforts to cash in on fellow left-backs Nuno Tavares — wanted by Nottingham Forest — and Kieran Tierney.