Aaron Ramsey will not feature for Arsenal until after the October international break as he continues to struggle with a hamstring injury.
Ramsey was one of the stars of Wales' run to the semi-finals of Euro 2016 but has been sidelined since suffering his strain during Arsenal's defeat to Liverpool on the opening weekend of the Premier League season.
Saturday's London derby against Chelsea is the latest fixture to come too soon for the 25-year-old, while Arsene Wenger does not expect him to be available for Wales' forthcoming World Cup qualifiers against Austria and Georgia.
The Arsenal boss told a pre-match news conference on Friday: "Aaron Ramsey is still struggling with his hamstring and I don't think that he will be available for our next game against Basel or at Burnley [next weekend], so before the break he will not be available.
"He has a small grade one hamstring but he is not completely free in his mind yet to push completely, so we stop him every time when he has a little pain.
"He is in the last days of his rehab and as long as he is not completely comfortable, we do not push him."
Ramsey's recovery is behind schedule from what Arsenal initially expected and Wenger conceded there is an element of added caution given the player's history of fitness struggles.
"We had a few disappointments because he was close to joining again and every time he is not completely ready," he added. "Not far [away], but we have to be cautious with him.
"It's nothing major, but I am a bit more cautious than I would be [with other players]. I would if he was ready to play, I would involve him in the squad of course, but he is not."
Wenger could be boosted by the return of Olivier Giroud from a toe injury to face Chelsea if the France striker suffers no reaction in training on Friday.
"Olivier Giroud has a test to see if he can be involved," he added. "He had a good training session yesterday so he is really the only one who could come back.
"I thought that he would be short for tomorrow. But we will see how he comes out of today's training session."