Although they can beat any team on their day, Portugal are prone to unexplained lapses and can be chronically wasteful in attack.
Portugal reached Brazil in style with Ronaldo netting all their goals over the two legs of a memorable 4-2 aggregate playoff win over Sweden.
But that performance masked a difficult qualification campaign in which they were held to unexpected draws by Northern Ireland and Israel and forced into the drama of a two-leg playoff after losing Group F's top spot to Russia.
It could have been even worse had Ronaldo not dug them out of a hole in the match away to Northern Ireland, scoring a second-half hat-trick in a 4-2 win after they had trailed 2-1 and been reduced to 10 men.
"We certainly had an inconsistent campaign. If that wasn't the case, we wouldn't have had to contest a playoff," said coach Paulo Bento.
"Even though we lost one of the games against Russia, we put in two good performances, but there were three other matches in which we didn't play so well."
Worryingly for Portugal, Ronaldo has suffered some nagging minor injuries in the run-up to the World Cup and was rested for their friendly against Greece in Lisbon and Portugal's training sessions after complaining of muscular pain in his left thigh.
After years of basing their game around a playmaker, firstly Rui Costa and then Deco, Portugal have changed their style to try and get the best out of Ronaldo.
Although they traditionally play a possession game, under Bento they have started to mix this with long passes into space for Ronaldo and Nani to run on to.
After Ronaldo, midfielder Joao Moutinho has become the most influential player in the team. The Monaco player is part of a fluid three-man midfield triangle which dictates the pace, tirelessly recovering balls and delivering pinpoint passes.
Joao Pereira and Fabio Coentrao are two energetic fullbacks who like to burst forward and, in Pepe and Bruno Alves, they have a fiery, intense pair of centre backs, sometimes too much so.
A big concern is the centre forward position where Helder Postiga and Hugo Almeida have been less than clinical.
The highly unpredictable Ricardo Quaresma would have been an interesting alternative, but was overlooked by Bento, the third World Cup in a row where he has been in contention for a place and has missed out.
There is plenty of experience in the side with Raul Meireles, Bruno Alves, Postiga, Pepe and Pereira all over 30 and one of the criticisms aimed at Bento is that he has been too conservative in his team selections.
For a small country, Portugal have had an exceptional record at big tournaments over the past decade, reaching the final at Euro 2004, the semi-finals at the 2006 World Cup, the quarter-finals of Euro 2008 and the semi-finals of Euro 2012.
Despite this, they have not always pleased the neutrals and ultimately they have not won anything either, losing to Greece in the 2004 final in their own Lisbon backyard when Brazilian Luiz Felipe Scolari was their coach.
But one thing that is in their favour this time is that other teams are regarded as favourites and, despite their old colonial connection with Brazil and a shared language, there will be very little pressure on them from the home fans.
Modern-day Brazilians have more in common with the culture of the U.S. rather than a distant European relation whose influence in South America has diminished over the decades since Portugal became economic, cultural and legal partners of the European Union.
There has often been a rough edge to Portugal's play and they were involved in a notorious game against the Netherlands in the 2006 World Cup which produced 16 yellow cards and four reds.
Portugal will certainly want to leave a better impression than they did in South Africa when they were involved in petulant goalless draws against Ivory Coast and Brazil.
They bowed out after a negative performance in a 1-0 defeat to Spain, marred by an incident at the end when Ronaldo appeared to spit at a television camera.