The Dutch secured top spot in Group F after beating Tunisia 3-1 on Thursday, finishing the opening stage with seven points and scoring 10 goals across their three matches.

However, Koeman insists that result is now behind them as his focus turns towards a difficult knockout tie against Morocco in Monterrey, Mexico.

"I'm not sure if we are the favourite in the match against Morocco," Koeman said. "We need to prepare for Morocco because it will be a big game. It's a good team with a lot of quality, and they can score easily."

The Netherlands manager has warned his players not to get carried away by their impressive group-stage performance, insisting the knockout rounds bring a completely different challenge.

"I don't think we're in a situation yet to think about that," Koeman explained. "We're going towards our real test, and that's what we're going to prepare for."

While the Netherlands have shown their attacking quality, Koeman knows his side must improve defensively before facing Morocco. The Dutch have conceded in seven consecutive matches, an issue the coach wants to solve before their next fixture.

"We do pay attention to that," he said. "One or two players are not in the right position, people aren't getting blocked, and that's the sort of thing we'll discuss with the players."

Despite those defensive concerns, Koeman remains confident in the team's attacking threat after scoring 10 goals during the group stage.

"Getting a goal against is part of the game, and we have scored 10 goals in three games as well," he said.

The Dutch coach believes his team can still improve by becoming more compact, creating more opportunities between the lines and reacting faster during transitions.

"The pace, the positions, to create more, to get more people in between the lines, and without the ball, we can be more compact sometimes," Koeman said. "We need to transition faster, or go back, or forward, all of us together. There is room for improvement."

The Netherlands will continue preparations in Kansas City before travelling to Mexico, where they will face Morocco in warm conditions at Monterrey Stadium.

"It's fine by me. It's a football country. It's interesting. It'll be hot," Koeman said. "We'll prepare really well."

Koeman has also praised the Dutch supporters who have created a memorable atmosphere during the tournament, with thousands of fans bringing their famous orange colours to the stadiums.

"You see so many orange shirts, and the songs that are being sung, and that gives you a fantastic feeling when you enter the stadium," he added.

With elimination waiting for the losing side, Koeman knows the importance of producing another strong performance against Morocco.

"We'll play well and win the match, because now if you lose you go home and if you win you stay in the tournament," he said. "And of course we want to go far in this tournament."

The Netherlands will meet Morocco on Monday, June 29.

Ronald Koeman - Morocco will be Netherlands' "biggest challenge" in World Cup knockouts