After impressing in recent tournaments, and with the world's most expensive player Cristiano Ronaldo on their side, Portugal started the campaign for South Africa 2010 as favourites to win Group One.
But a 3-2 home defeat by Denmark, two scoreless draws against Sweden and inconsistent displays have deflated belief in Carlos Queiroz's side.
"We are not there yet. We won this game (on Saturday) and ... that has to be transported to the game in Guimaraes on Wednesday," Queiroz told reporters.
"We know they are a weaker team than us. But we have to prove that on the pitch," said right back Jose Bosingwa.
"We know they are very defensive but we will try to score so they open up."
Portugal's poor finishing has let them down in big matches, most notably in the draws against Sweden and the draw in Denmark when they failed to cap an ultra-attacking first-half display with goals.
Queiroz brought in Liedson, Sporting's Brazilian-born striker who recently obtained Portuguese citizenship, after that match. He scored two goals in three games and poses the main threat to Malta's defence.
Queiroz's toughest decision may be in midfield, with Pepe back from suspension and competing against Pedro Mendes who responded to a surprise late call-up with a fine performance against Hungary.
