After Poland's 1-0 defeat of Ukraine secured it a slot in the last 16, coach Adam Nawalka said star striker Robert Lewandowski's third straight blank at Euro 2016 is not a concern.

"The fact that Lewandowski has not scored a goal yet is not a problem for either me or the team," Nawalka told media in Marseille's Stade Velodrome on Tuesday.

"It is a matter of time, I think he will score in the next game," he said.