They still have some able players to call upon though.
The Gunners have endured a mixed start to the Premier League season following two victories and two losses to leave Arsene Wenger's side in mid-table.
The Arsenal manager said, "a few players have had some response to playing two worldwide games like Ozil and Ramsey, so they are rested completely".
Petr Cech, Laurent Koscielny, Aaron Ramsey, Granit Xhaka, Mesut Ozil, Danny Welbeck and Alexandre Lacazette all sat out the open training session on Wednesday.
'In three days, you can recover'.
That could open the door for Jack Wilshere to make his first start for Arsenal in over 13 months as he looks to rebuild his career following another fractured leg.
"In training he is getting stronger, that's what we want", Wenger said of the midfielder.
FC Koln are yet to win a match in England, having previously played five times in the country (D2 L3) - overall W2 D4 L6.
One of the most polarised figures at Arsenal despite his exemplary record for the club, Giroud seems to be at a crossroads at Emirates now. Sometimes it takes time while other clubs use money. "He was injured at the end of last season so he came back later than everybody else".
He was supposed to be Arsenal's saviour and future captain for many years to come but very little has gone to plan for Jack Wilshere thus far.
"The disadvantage is of course that he was out of the game for a long time, but there are advantages as well", he said.
"Teams like Leicester and Chelsea, they didn't have any midweek games [when they won the Premier League] so obviously players will get more rest and just play at the weekend".
"Every game is an opportunity for him and this season".
In the attacking third, the likes of Theo Walcott and Alexis Sanchez will probably get the nod to start behind Olivier Giroud.
The Hard Tackle, therefore, predicts a hard-fought 1-0 win for the North London outfit to kickstart their Europa League campaign on a positive note.