The Dutch enjoyed a comfortable 3-0 victory in their round of 16 game to show a major improvement after squeezing through the first phase in third position in their group.

“It shouldn’t be that we need a defeat to spark a good performance and come out of our shell,” said Koeman of the triumph over Romania, which followed a 3-2 loss to Austria.

“But we created a lot of chances and showed a lot of speed up front. It was good game even if the opponent gave us a lot of room.”

Koeman warned, however, that Turkey would be a tougher proposition.

“This is a different opponent with different qualities. They have played with four at the back, but also with five. Just like the Romanians, they showed a lot of heart in how they play. But we are more worried about ourselves.

“We are playing in Berlin for a semi-final, a great opportunity to progress even further in the tournament. But we're not just going to romp to a win, that certainly won’t be the case. It's going to be a very difficult game," he told Friday’s pre-match press conference.

Koeman said he felt Turkey would offer his side space to exploit. “We’ve just got to be patient with the ball and keep possession,” he said.

"The Turks are very enthusiastic and good on the ball. They have also seen us against Romania and will probably look to have our measure.”

Koeman said it had not been an easy tournament for the fancied sides. “All the big teams have struggled at different times. England needed a late goal to survive, Portugal went through on penalties. You have to fight all the way.”

The Netherlands will give Steven Bergwijn a late fitness test on Saturday morning as he struggles with a knee injury, but Koeman said key defender Nathan Ake was fit to play after battling with niggles over the last few days.