It is a very important match to start the Europa League on the right foot.
Arsenal's first match in the competition is against German side Cologne.
As for Arsenal, they bounced back from a 4-0 drumming at Liverpool beating Bournemouth 3-0 last time out in the Premier League. They had a hard time too, they lost two games and won several games in the last minutes (against West Ham and Watford).
Arsene Wenger seems set to shake up his side for the Cologne game.
Petr Cech, Laurent Koscielny, Alexandre Lacazette, Danny Welbeck, Mesut Ozil, Aaron Ramsey and Granit Xhaka were all absent at London Colney, appearing to confirm that they will all sit out of the Gunners' opening Europa League encounter.
According to The Independent, the players were excused from training on Wednesday morning as they will not be involved on Thursday.
"Now we have to continue, we have to rest tomorrow and then to start to think about the next game, a strong game, a tough game against Arsenal (on Sunday)".
Manchester City were thought to be keen on signing Sanchez before the transfer window closed, but Arsenal refused to sell their talisman and instead kept hold of the 28-year-old.
David Ospina should also line up in goal, while Theo Walcott should also be included in the starting XI.