Rhône: Northern Ireland face Ukraine in Lyon on Thursday with both sides needing a win to keep their Euro 2016 knockout-stage dreams alive in what Irish boss Michael O`Neill dubbed a `Cup final`.
Having seen his side`s 12-match unbeaten run ended by a 1-0 defeat to Poland on Sunday, O`Neill expects a big improvement for their second outing in a first major international tournament for 30 years.
"We have to treat this like a Cup final, because we know the significance of the three points." said O`Neill.
"We`ll have to be at our very, very best to win and be better in a lot of aspects."
With world champions Germany next up in Tuesday`s final Group C game, the Irish must avoid defeat to retain realistic ambitions of making the last 16.
"Our goal remains to go into the last game with something to play for. Hopefully, Germany will have six points by then and may be looking ahead to future tasks.
Northern Ireland captain Steve Davis said they must "take the negatives from the Poland game and turn them into positives," while defender Jonny Evans urged his side to be bold.
"To give ourselves the best chance (to progress) we are going to have to go out and win. It makes it exciting because Ukraine are in the same position," said ex-Manchester United defender Evans.
"You`ll see a lot more aggression, a lot more pressing on the opposition, giving them less time on the ball.
"That`s something we`ve been good at in the past and we want to get back doing that."
Northern Ireland`s build-up has been overshadowed by the tragedy involving a young fan who fell to his death in Nice in the early hours of Monday morning.
The Irish fans are planning a round of applause at the Stade de Lyon in the 24th-minute of the Group C clash to pay their respects to 24-year-old deceased Darren Rodgers.
O`Neill has described Rodgers` death as "devastating" as they prepare for their key clash.
On the field, though, Goalkeeper Michael McGovern, who impressed in Sunday`s defeat when Arkadiusz Milik`s goal condemned O`Neill`s men to a narrow defeat, is favourite to start between the posts ahead of 38-year-old veteran Roy Carroll.Ukraine have never lost to yet to Northern Ireland, with two wins and two draws in previous meetings, but also arrive in Lyon on the back of a defeat after going down 2-0 to Germany.
And captain Artem Fedetskyi expects another tough fight against the British minnows with so much at stake for both sides.
"It`s going to be a decisive game for both teams, they are very dangerous at set-pieces and we`ll need to take all chances we get," said Fedetskyi.
AC Milan legend Andriy Shevchenko, now Ukraine assistant coach, also expects the biggest threat from the Irish to come from set-pieces.
"Northern Ireland`s strengths are great fighting spirit, like in all British teams, set-pieces, defensive organisation and counter-attacks," said the ex-Chelsea star.
"They try to play very compact and make fast transitions."
Meanwhile, Dynamo Kiev midfielder Serhiy Sydorchuk acknowledged the game is effectively a final for both sides.
"Now all our thoughts are on Northern Ireland. This is the most important game for us so far," said the 25-year-old.
"Maybe we weren`t confident enough at the beginning of the Germany match, but then we saw they were also just men of flesh and blood.
"Now we are definitely not afraid of anyone."