Morocco will meet the Dutch team on Monday in the Round of 32 at Monterrey Stadium in Guadalupe, Mexico, with Diaz expected to play a key role after becoming one of the nation's most important attacking figures during the tournament.
The 25-year-old has started all three of Morocco's group matches and has already made his mark by providing two assists in important moments to help his team reach the knockout rounds.
Ouahbi believes the Real Madrid star has even more to offer and expects him to produce his best football when the pressure increases.
"He's assisted two decisive goals at crucial moments. This Monday we'll see an even better version of him," Ouahbi said. "He's the kind of player who steps up when it matters most."
Morocco reached the knockout stage after an encouraging group campaign. They began with a 1-1 draw against Brazil before recording a narrow 1-0 victory over Scotland. A convincing 4-2 win against Haiti then secured their qualification and confirmed their place in the next round.
However, Ouahbi knows his team face a difficult challenge against the Netherlands, who also impressed during the group stage. The Dutch topped their group after drawing 2-2 with Japan, beating Sweden 5-1 and defeating Tunisia 3-1.
The Morocco coach admitted the Netherlands will provide a different test but insisted his players are ready for the challenge.
"I have confidence in my team and in what the players have shown in training," Ouahbi said. "The Netherlands has a different profile compared to our previous rivals, but we will stay true to our style and adapt to any problems that may arise."
