Timber, signed for 40 million euros ($43.52 million) on a long-term deal from Ajax, is sidelined after suffering a knee injury during Arsenal's season-opening home win over Nottingham Forest and is set to undergo surgery.

"After just joining to have this injury is a big blow for him. We recruited him intentionally to add to the team and now we have to adapt and move on," Arteta told reporters.

"He has been very good, to be honest. He's a special character. He's in a good place, so we are all willing to help him, but it's going to be a long journey," he added on Thursday.

"I'm thinking about the resources we have in the team but he would have given us different things on both sides of defence. It's an opportunity for everybody. We need everybody."

Arteta has helped Arsenal qualify for the Champions League for the first time since the 2016-17 campaign and last season's Premier League runners-up this month won the Community Shield season curtain-raiser by beating treble winners Manchester City.

Arsenal have tried to add depth to their squad with new signings to challenge for the title again but Arteta said they do not have a number one in any position, while also not ruling out doing more business in the transfer window.

"It's never my decision (transfers), it's one we make as a club with other people involved. There are always other elements to that," Arteta said.

"My focus is on getting the best out of the squad we have now. We are always open in the transfer market both ways."

Arteta said he was hopeful that Ukraine defender Oleksandr Zinchenko, who has been out with a calf problem since May, will be available soon after joining team training.