Ozil has been axed from both the Premier League and Europa League squads by manager Mikel Arteta.
But Koscielny told L'Equipe: "We're both part of the 'Arsene Wenger Generation'.
"The coach loved him as a player. It was more complicated with Unai Emery and Mikel Arteta.
"Knowing him, he must always be professional in training, always on time. He is undoubtedly at the level demanded by the Premier League.
"There is probably a certain case with the club since last year, I hope both sides find a deal that works for everyone. He is a competitor. I hope to see him back on the pitch soon, at "As a man, he's a very good person, who got along with all his teammates. He gave a lot, helped sick children. He is a generous person, with whom I got along very well.
"As a player, he is in my opinion a phenomenon. He can find passes that no one sees, he's a maestro. He can rock a game with incredible passes."