So impressive have his performances been in training that Wenger has changed his mind as he is keen to see more of the centre back.
"He looked comfortable technically, he looks very mobile as a defender and he looks very pacy and strong in all aspects of defending," the Arsenal manager said.
"What I don't know yet is how well he'll cope with pressure, how much his lack of experience will be detrimental to his performances.
"When you go to a big club, every game and every mistake is analysed. Every action you take in the game is analysed, so you're under scrutiny and that puts a huge pressure on you. If you make a mistake in a smaller league for a smaller club, it's less of a story than it would be at a big club.
"We will see [how he copes with that] that in the games and I haven't seen him play in England against an English team yet. I have to see that. Personally, I am encouraged by what I've seen and I've decided to keep him until May.
"Greece is a fantastic sporting country. Their basketball and football is absolutely amazing. They have a real knowledge of team sport and they produce fantastic players. He can be one of them from what I've seen, if he develops well.
"He looks like an intelligent boy as well, so let's hope he will develop into a great player in the future for Greece."