Known around the club as Dinos, the Greek defender is again spending the season out on loan with Stuttgart.
The centre back played 22 times for the German club last term, impressing as they finished ninth in the Bundesliga. The loan deal was extended by 12 months in the summer, with an option to make the move permanent at the end of the campaign.
The classy defender also made his senior debut for the national team last season, in a friendly against Honduras.
Signing for Arsenal in January 2018, he made his first-team debut at Manchester United before injury interrupted his progress. .