Shkodran Mustafi will miss Arsenal's trip to Southampton on Sunday as the defender has not recovered from a thigh injury, Press Association Sport reports.
The Germany international was forced off early on in last weekend's 3-1 defeat to Manchester United and will sit out the game at St Mary's.
Mustafi, who made a mistake to allow Jesse Lingard to put United 2-0 ahead inside the opening 11 minutes at the Emirates Stadium, had been enjoying arguably his strongest spell in the Arsenal side since joining from Valencia in the summer of 2016.
The 25-year-old has looked more secure in the three-man defence Arsene Wenger has largely fielded since towards the end of last season
"It is a possibility,'' Wenger said earlier in the week when asked if Mustafi could play at Southampton. "It is a little thigh problem. A small one.''
But Press Association Sport now reports that Mustafi will definitely miss the game on the south coast.
Wenger seemingly pre-empted that news as he opted not to field Per Mertesacker in Thursday's 6-0 Europa League victory over BATE Borisov.
That means the 33-year-old Arsenal captain will be well rested to make a rare Premier League start in Sunday's game.
Mustafi reportedly came very close to leaving Arsenal in the summer, but constant links with Inter Milan failed to materialise into a move.
He has split opinion since his reported £35 million move from Valencia, but fellow defender Laurent Koscielny said recently that Mustafi has improved since he came back from a recent injury.
"He was injured for a long time and I think he was angry,'' he said. "It is normal to be hurt when you are out for two months. It is very difficult for a player to stay outside of the team.
"He just came back and showed he wants to help the team and to win. That is what we want: to show on the pitch which way you want to go. Shkodran, for the last two games, showed to his teammates he wants to win and give everything on the pitch.''
Santi Cazorla is the only other injury absentee for Arsenal, with Wenger admitting that the midfielder is back at "zero" having required another operation on his problematic ankle issue.