The former Southampton defender was signed by the Gunners last week.
"Can he play every week? Maybe not, he is 19 years old but he can play a major role," Wenger said.
"He has the qualities to impose his quality in this part of the team (central defence) and I believe he can play in defensive midfield as well.
"I believe he is good value for money. He is 19 and a promising talent.
"As a manager you believe in the players when you buy them - we spent a lot of money on him but overall, in the long-term, it is money well spent.
"When the players play at the top for a long period you can never say it's expensive. It is expensive now but I don't regret it."
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