The 23-year-old has been at the Bundesliga club since last summer.
He has excelled this season, and Mislintat hopes he can extend the loan deal for the Greek centre-back for another season.
"We're super happy that he's been a regular starter in recent weeks," Mislintat told The Athletic.
"We would like to keep him on loan one more season, if possible. But that will be down to Arsenal.
"He has all the hardware and all the software to be a great defender.
"He has been unfortunate, he's got a lot of injuries. A pubic bone inflammation kept him out more or less for one and a half years.
"The moment we thought we could play him, he tore his meniscus. It's important for us to get him fully match fit. If he can stabilise physically, he's undoubtedly a Bundesliga-level defender.
"He's one of the fastest centre-backs in the league alongside Dayot Upamecano.
"A super guy, a model professional. You have to admire his energy, all the strength it took to get over his injuries."
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