Portugal are in a two-horse race with Switzerland to top Group B and clinch an automatic place in Russia, with the side managed by Fernando Santos currently three points below the Swiss with only two matches remaining.
They are both guaranteed to at least finish second and thus qualify for the play-off round, but Portugal will feel they are more deserving of a first-place finish to avoid potential surprises. Their place in Russia is by no means certain, but they do depend on themselves.
Settling for second and going the play-off route would see them risk facing the likes of the Netherlands, Wales, Croatia or Italy, fierce competition in the two-legged tie to make it to the World Cup.
Tensions are reaching fever pitch in Portugal as they head into vital fixtures in the coming days. The odds are in their favour as they travel to Andorra on Saturday, especially after dismantling the Principality 6-0 in the reverse clash. Real Madrid star Cristiano Ronaldo, who was responsible for four of those goals, is available and eager to recover the goalscoring form he has been lacking in La Liga.
His side will need him more than ever when they host Switzerland in Lisbon on Tuesday. It is not the first time Ronaldo's heroics pull his national team into competition and, having scored 14 goals so far in qualification, the 32-year-old shoulders a heavy burden to deliver.
The Portuguese stars could be tempted to disregard Saturday's clash, focusing more on beating the group leaders in Tuesday's decider. But as manager Santos underlined the importance of both games, warning: 'We've two decisive games. If we don't win the semi-final against Andorra, there won't be a final against Switzerland'.
Portugal will look to avoid making the same mistakes as Leo Messi's Argentina, who no longer depend on themselves to qualify in the final round. Portugal will require back-to-back wins to ensure their participation next summer and to do so they are banking on their captain and leader, Cristiano Ronaldo.