Sergio Conceicao says Portugal have learnt from their mistakes in the shock 3-2 defeat by the United States and it would be "a crime" if they did not qualify for the World Cup's last 16.
"We will be better on the pitch and you will doubtless see a different team," midfielder Conceicao said after a training session at Seoul's military academy on Friday.
"I believe that as a team we think as one and the motivation of just being in the World Cup has to be the most important factor, and gives us the will to win."
Portugal must beat both a physical Polish side in Chonju on Monday and then co-hosts South Korea in Inchon on June 14 to be sure of moving forward to the second round.
"In mental terms there will be a difference, and maybe even a bit of an improvement in physical terms, but it will be difficult," Conceicao said.
"We are very impatient and wish we could play right now, so that we could show as soon as possible what we can do.
"We have the best range of players that Portugal has had in recent years, and it would be a crime if we didn't achieve what we could."
The feeling in the Portuguese camp is that they were nervous and over-confident against the Americans.
"We started out too anxiously to show we're the best. We maybe thought the group was too easy. That was the feeling in Portugal. But in a World Cup, nothing's easy," Conceicao said.
"We need to keep things simple and work for each other."
There was good news from the camp about the state of Luis Figo's ankle.
Out of action for two months this season with a partially torn ankle ligament, he apparently felt no pain during Wednesday's defeat.
But team doctor Henrique Jones said the Fifa World Player of the Year was still not fully fit.
"I can tell you once and for all that the first thing Luis Figo told us after the USA game was that he had not had any pain in his ankle," Jones said.
"Obviously, Luis Figo, as you know, has not been fully training over the past two months and it is probable that, in overall physical terms, he is not 100 per cent fit."