The player is loaned to Arsenal from Real Madrid and got injured this past 6th November in a Europa League game against Vitoria de Setubal.
This means that he will miss out on the next two Premier League games and also in Friday's game against Eintracht Frankfurt.
In addition to the European game, Ceballos will not play the games against Norwich City and Brighton and Hove Albion and Standard Liege, at the very least.