Alex Iwobi has impressed during his stint in the line-up and Arsene Wenger could continue to show faith in the Nigerian forward.
I'm sure the boss will give Koscielny every opportunity to prove his fitness after Shkodran Mustafi was ruled out for up to six weeks with a hamstring injury that he picked up during the global break.
The Gunners have numerous defensive concerns ahead of Saturday's Premier League encounter, with Mustafi having picked up a long-term injury while playing for Germany while Koscielny has been out with an Achilles problem.
The news of Mustafi's injury may not be too much of a blow to Wenger though considering he hasn't featured for the Gunners so far this season.More news: Kelly: Barring 'change,' he's not quitting or being fired
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"It is always hard to predict the situation because the player I least expected to lose during the break was Mustafi", Wenger said.
"If he has no pain on his Achilles then he will play".
"I will decide what I have to do when Koscielny has his test tomorrow".
Midfield: Sead Kolasinac is a minor doubt with a hip injury but the Bosnian worldwide is expected to be available while Hector Bellerin should keep his place on the opposite flank. He trained on his own and the first signs are positive.
Wenger, meanwhile, will make a late decision on the make up of his front three for the game against Marco Silva's men. Sanchez won't be back with us until tomorrow.