The Germany international is off contract in June, as is another Juve target - Schalke midfielder Leon Goretzka.
“We have no deep problems, but we have to look ahead, knowing that we need to be competitive and seize any opportunities that the market offers us," he said.
“It's not easy, and when you have to sign a player for Juventus. It's not easy to find them.
“It's also true that we need to reflect on this squad, in terms of age, but we also realise that we have great professionals.