The 19 year-old played the full 90 minutes on Monday (AEDT) as Ajax thrashed Excelsior 7-1 in Rotterdam, just four days on from a hard-fought 1-1 Champions League draw with Benfica.

Speaking afterwards, De Ligt told Fox Sports: "To be honest, we didn't play at 100 per cent, but we won 7-1. The difference between the sides in the Eredivisie right now is huge.

"The tension is less each time as there's only two teams who are racking up the points. If we keep winning, it won't be a problem, but we have to admit that it's less fun."

De Ligt has been heavily linked with a move to Barcelona, having impressed in the Ajax first team since making his debut two years ago.

Koeman, who joined the Catalans as a player in 1989 after spells with Groningen, Ajax and PSV in the Netherlands, can see why De Ligt may want to leave his homeland.

"I just spoke with Matthijs de Ligt about the fact that he thinks he doesn't get challenged a lot in the Dutch league," Koeman said. "I didn't know that he said that in the press, but I can imagine he thinks like that.

"It says a lot about the level of the Dutch league. I can imagine when you first play in the Champions League and then at Excelsior away, on artificial grass. Then, you have to challenge yourself.

"You expect that from every player, but it's difficult. The intensity in the Dutch league is a lot less, just like the competition. He can go into every match like it's a final. But the atmosphere, the stadium, the pitch... it's all different."

When asked if he thinks it is important for De Ligt to move to a tougher league, Koeman replied: "I think it's clear that a player like Matthijs de Ligt in a certain moment decides to make a step to a bigger league, to another level. Unfortunately, players leave the Netherlands earlier than in my time."

Netherlands is preparing for Nations League matches with France and Germany over the next week, for which Koeman handed a first senior call-up to Hertha Berlin winger Javairo Dilrosun.

"In the Under-21s, they were very positive about Javairo Dilrosun," Koeman said. "Now that [Arnaut] Groeneveld is injured, we needed to look for a solution.

"In the last couple of weeks, we followed Dilrosun and we were very positive about him. He showed in games against RB Leipzig and Borussia Dortmund away that he is a great talent. I'm going to meet this 'sweet boy' now for the very first time. I'm curious."