The Crystal Palace winger was surprisingly selected by Roy Hodgson after a number of withdrawals and Hamren admitted he has no knowledge of the Three Lions' latest recruit, even mistaking him for Sunderland's French striker Louis Saha.
"Wilfried Zaha? I know Saha, but I don't know if it's the right one,” Hamren told reporters.
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"No, I don't know about him. Sometimes you get carried away. Sometimes. But that's also something that, in sport, we need those heroes or those stars.
"Sometimes, you make a star too early. It's better to make him a star when he is a star in world football. I hope he's not a star tomorrow but in the future.
"We have a lot of 'new Zlatans' here in Sweden. Maybe he's the new Zlatan [Ibrahimovic]. Maybe. But, so far, we only have one Zlatan."
Hamren went on to confirm that one of his scouting team will help him assess the dangers the 20-year-old might pose to his team.
When asked if he would be getting a report on Zaha, the 55-year-old added: "Of course, when you have a young and inexperienced player, there have to be some changes.
"I'm sure he'll want to play his way of football too. I hope I don't have a bad surprise tomorrow with the player."
Hamren also hailed Three Lions coach Hodgson, who has spent a large part of his football in Scandinavia, revealing the amount of respect held for the former Fulham boss from all in the Swedish game.
"Roy Hodgson has a good reputation here," he said. "I really like him as a coach and as a person. He's someone I've always spoken to. I was a young coach when I first met him and he gave me his knowledge and experience.
"He has been really good for Swedish football and a really big name in Sweden in football, acclaimed by all our coaches who have learned a lot from him.
"There's big respect for him."