Ronald Koeman says Matthijs de Ligt needs to adapt to a new way of defending with Juventus.

The centre-back joined the Serie A champions in July for an initial fee of €75million after a standout season with Champions League semi-finalists Ajax.

He endured a tough debut in Italy's top flight in Juve's dramatic 4-3 win over Napoli but has shown some encouraging signs of a blossoming partnership with Leonardo Bonucci in recent weeks.

Koeman thinks the 20-year-old still needs to take lessons from the "Italian school" of defending, but the Netherlands boss is not surprised to see a player so young still have room for improvement.

"I'm always a big advocate for adapting to your new team, your new country and your new team-mates," Koeman told reporters. "I think he really does need to adapt to a new way of defending, because it's different from the way he played at Ajax. Maybe that's the 'Italian school'.

"Bonucci said the same: he also needs to adapt to this kind of zonal marking [under head coach Maurizio Sarri] instead of the way they defended under [Massimiliano] Allegri. I think Matthijs needs time. But he's already so good at this age. It would be weird if he didn't have to learn anymore.

"Just before the last international break, there was lots of criticism, but he still played really well with the national team. I think this is a very nice environment for him. But with time, I think he'll learn how to adapt to his new position at Juventus as well. I think he can reach a very high level both in our team and at Juventus."

De Ligt's focus for now is on helping Netherlands in their bid to qualify for Euro 2020.

Oranje meet Northern Ireland and Belarus in the international break and will look to close the three-point gap to leaders Germany at the top of Group C.

Koeman is confident in his side's chances of progressing as he considers their squad, particularly their attack, a rival for the world's finest teams.

"I think we have a squad that is equal to the squads of other countries - and I'm talking about the best countries in the world," he said.

"That's also thanks to the development of our attacking players and upcoming talents that aren't with the squad yet. They are so creative, dynamic and quick that they make us more dangerous offensively.

"In the past, that's where we had some problems. But that's also one of the reasons why we selected so many attackers [seven] and only five midfielders instead of six and more attackers. We have more choice than ever before."

Netherlands host Northern Ireland, who are also three points ahead of them, on Thursday before facing Belarus three days later.