Mikel Arteta confirmed Matteo Guendouzi was dropped for Sunday's 4-0 Premier League win over Newcastle United due to his attitude in training.
Speaking at a news conference ahead of his side's Europa League clash with Olympiacos on Thursday, Arteta revealed the 20-year-old's absence was related to issues with how he was training.
"I just do my team selection in regards to how they train, how they play, how they behave and every week it will be different," he said.
"One week it will be one reason, one week it will be another reason. It was about the way we trained, the way we live and I want the best players for the game and I select them in relation to what I see on a daily basis."
As we all know the young French man has an explosive attitude. We've seen him not once to fight with other players during Arsenal games.
Guendouzi has been named in Arteta's squad for the last-32 first-leg clash in Athens, but the Spaniard refused to confirm if he will be selected in the starting XI.