Spain head into the encounter in Braga second in Group E, two points adrift of leaders Portugal heading into the final game.
"We have planned this game as if it were a quarterfinal in Qatar," Luis Enrique said in a news conference on Monday.
"It's 90 minutes and we need to win, not even a draw will do. It's positive that we reach the sixth round of the Nations League with a possibility to finish top and qualify for the final four.
"It is a final, it is beautiful. I'm certain that against Portugal we will be up to the task."
"This is football and there are no friendly games," Luis Enrique said.
"The level of demand in national team football has changed, take a look at the rest of the results."
Fellow European nations France, England and Germany, who will compete with Spain and Portugal in the World Cup, have all struggled in the Nations League but Luis Enrique said they are contenders to win in Qatar.
"Just like the top national teams in Europe. Does anyone dare to say that England or France will not be favourites in the World Cup?"
The 52-year-old added that Spain will be put to the test by Portugal.
"We have always defined them as very talented and with an outstanding physique," Luis Enrique said of Portugal's squad.
"They have already achieved very important things. They are more established as a team [...] our idea is to keep growing.
"We have played three recent games against them, and we played well even if we didn't win, we drew all three."
Pablo Sarabia, who has featured in all of Spain's Nations League games, agreed.
"All of the games we have played against Portugal have been difficult," the Paris Saint-Germain winger said.
"Portugal have great individual talent and technical quality. We have to do things right in order to win this game and reach the Final Four.
"We have full confidence in all of the members of this squad. The strength of this team is the group."