England Under-21 boss Aidy Boothroyd has labelled their Slovakia showdown as must win.
The Young Lions head into their second Euro 2017 game on Monday after Friday's opening 0-0 draw against holders Sweden.
Defeat would leave their Group A qualification hopes hanging by a thread with leaders Slovakia having already beaten hosts Poland 2-1 on Friday.
Only the group winners and best runner-up from the three pools go through to the semifinals and Boothroyd knows England cannot afford to let Slovakia get out of sight.
He said: "It's knockout football now without a doubt. We've got to win and then win and win the next one after that. But we have to beat the Slovakians first.
"They have had a brilliant start. They're a very good team and I've been really impressed with them. Their game with Poland was probably better to watch than our game with Sweden and it will be difficult. We totally respect the result they got.
"We have to go full pelt for every game but at the same time because of the squad that we've got I've got to think about using everyone that's in it.
"But we have to win so I've got to pick the best team, even if some of them might be a bit tired they might have to play a smaller part in the game and think about what goes on in the last half hour of the game.''
Senior boss Gareth Southgate, assistant Steve Holland and technical director Dan Ashworth are all in Kielce after arriving for the Sweden game on Friday.
Southgate watched training on Sunday and Boothroyd believes it shows the players there is an opportunity to step up to the senior side.
"It's really helpful having them here. It's great that Gareth, Steve and Dan are here because it shows players there is a pathway for them,'' he said.
"And if the senior manager can take time out of his busy schedule to come to watch us then it gives the players a boost. Gareth's been very positive. We are very close anyway.
"It's great, if I have any questions about players Gareth can be my sounding board because he knows them all so well and was with them in Toulon.''
And England Under-21 captain James Ward-Prowse has revealed that Southgate has been offering advice ahead of their clash with Slovakia.
Ward-Prowse was also captain for the Under-21s under Southgate -- who gave the 22-year-old his senior debut in March -- and revealed Southgate has been helping to guide the squad.
"He's been around and spoken to us, pulled us aside individually and seen how we are, and it's great to have him and Steve (Holland, assistant) around,'' said the Southampton man. "They played a massive part in our qualifying campaign to get us here.
"He wants to show us support and give us that confidence. It was great to see him here, to show us there is a pathway for young English players.
"We have a lot of friends in the seniors now and it is a time for us to show him what we can do individually and as a team.''
While Ward-Prowse has been away Southampton sacked Claude Puel as manager but the midfielder is refusing to let the St Mary's uncertainty upset his plans with England.
He said: "It is one of those things and it is a decision from the club that has been made. Claude was very good to me, he gave me lots of opportunities and I got into the England squad while playing under him.
"I have got nothing but thanks for him. But my main focus at the minute is the tournament and making sure I am in the best way mentally and physically to help the team. I haven't spoken to him.
"The tournament is the main priority, as I said. It seems to happen every summer [that Southampton lose their manager] but that is the way football is sometimes.
"It is up to us as players to deal with it. The club and the players have shown that we can cope with managers and players going.''