While Kozak believes that England have a quality squad, he thinks that his side are equal to fellow Group B contenders Wales and Russia.
"The top favourite [in the group] is England because they have a large squad of very good quality players," Kozak told reporters. "But this is a tournament and the pressure is on their young players. I am curious how they react to that pressure.
"I think it will be even between the rest of us because Wales, Slovakia and Russia all has quality. It depends on the day because I do not see much difference between these teams."
Slovakia will face England in their final group game on June 20.