Cristiano Ronaldo and his men have been held to two draws so far against inferior opposition and are now in serious danger of not topping their group.
Hungary are all but assured of their place in the next round, as they sit two points clear following victory against Austria and a draw with Iceland, while Portugal still have work to do.
Bernd Storck's men have arguably been the most surprising team in the tournament, and victory against Portugal would rank among the great Euro upsets.
England lie in wait for the team who finishes second in Group F.
Before the tournament began, this would have been seen as a chance for Portugal to rest players. But as they are not guaranteed of a second-round berth, the big guns will all line up.
Cristiano Ronaldo and Nani will continue to lead the line, although Ricardo Quaresma's ineffective display against Austria puts his place in doubt.
Renato Sanches could start in midfield after two promising displays from the bench.
Hungary may be forced to rest veteran midfielder Zoltan Gera, who started both of their previous games, while Tamas Priskin is set to lead the line once more.
Ones to Watch
Portugal: Andre Gomes
Fresh off the back of an outstanding season in Spain, Andre Gomes could be the man with the key as Portugal look to unlock Hungary's tight defence.
The creative midfielder has had a promising tournament so far but Portugal are yet to click into gear up front, as Cristiano Ronaldo and Nani continue to waste chances.
The importance of Gomes has increased as they seek to go through, with chances and goals paramount against a Hungary side likely to sit back and defend.
"We were on top, we were the better team but we couldn't translate that superiority into goals," said fellow midfielder Joao Moutinho after their draw with Austria.
"We wanted to win, our individual quality was good, but I'm sure all team-mates would trade that for a victory.
"In both games we had enough chances but weren't able to score more. We still believe in our potential. We have to take our opportunities and when we do, we'll win by more than one goal."
Hungary: Balazs Dzsudzsak
While Portugal target goals and a win, Hungary's game plan will be to sit back and frustrate the opposition, just as they have done to Austria and Iceland so far.
Captain Balazs Dzsudzsak is vital to their success, as he leads by example and sets the tone for their displays from his place on the wing.
And on the few occasions they do venture forward, the Bursaspor winger will be key as his pace, skills and ability to score will threaten Portugal's defence.
"It is still unbelievable to be talking about things like this," he said.
"We are exceeding all our expectations and dreams; we Hungarians came to the Euros knowing that just taking part was a dream.
"We are proving that our qualification was no accident, and we deserve credit because nobody would have thought we would be top on four points at this stage.
"Our aim is to stay disciplined and we will see what ha