England also play Croatia on Wednesday and Boothroyd, who is out of contract in the summer, conceded Sunday's showdown is his most vital assignment.

"Without a doubt, the next game is always the most important one but when you are in a tournament it ramps it right up," he said.

"This situation is part of the development and growth of our players. The opportunity is there, the players know, the staff know, I know the importance of it.

"I feel very fortunate to represent my country and work with the best players in Europe and in the world. They are young boys and still learning.

"Is it an important game for me? It's an important game for England Under-21s, we are still in there fighting and we won't go down without a fight."

Boothroyd has no injury worries but is likely to make changes and PSV Eindhoven attacker Noni Madueke will make his debut.

The manager was unhappy with the Young Lions' lack of attacking punch in Koper and wants that to change on Sunday.

"We are a team who like to pride ourselves on creative football and goals we're expected to score," he said.

"We were a blunt instrument which was not like us. We've talked about that, there was quite a bit of reflection. We have had a blip in the road but if it was easy it wouldn't be worth doing.

"The players have been reminded about the importance of how we play the game. We were a bit irritated with what we got against Switzerland.

"We came here to win two games out of three, ideally three, but we're still on track. We have to pull ourselves together and get cracking for the next game."

"There's no time for being moody."