Isak endured an injury-disrupted debut season at Liverpool, missing the majority of the campaign after joining the club from Newcastle United, but he has since regained fitness and opened his World Cup account in Sweden's 5-1 demolition of Tunisia.
"We were very happy that he returned and at the end he was fit, he scored some goals and he played well. And obviously he started the tournament very well with his performance," Gakpo told reporters.
"I think everybody knows how good a player he is. So we need to look out for him," he added.
Gakpo acknowledged the Dutch need to win after drawing 2-2 with Japan in their debut, but dismissed talk of added pressure as they prepare to face a confident Sweden side, whose forwards Isak and Viktor Gyokeres impressed against Tunisia.
"We know that we have to win the games because we want to go through the group stage. Obviously the result for Sweden was very good for them, but we have to see that separate and just focus on ourselves, what we can improve," the 27-year-old forward said.
Gakpo said the Netherlands would take lessons from their opener against a disciplined Japanese defence, particularly in dealing with tight spaces.
"I think it could be the same, but maybe Sweden's set-up is a little bit different. I think we will analyse that tomorrow. And then we have to make a game plan for that as well to see how we can try to create a lot of chances," he said.
The Netherlands face Sweden in Houston on Saturday, while Tunisia and Japan meet in Monterrey later the same day.
FIFA World Cup 2026
The 2026 World Cup will be held from June 11th to July 19th in the United States, Canada and Mexico. The tournament will feature 48 national teams and will be played in 16 modern stadiums.
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