Thomas joined Arsenal in the summer window this season. In the game against Manchester City, he played 81 minutes to complete his league debut.
Now he has gone to Vienna with the team to prepare for a quick Europa League match against Vienna, and is expected to complete his European debut at Arsenal.
Because the training time with the team was too late, he only played for about 10 minutes in the Manchester City game. After the game, Arteta also said: "Thomas will be able to play with us soon."