Switzerland kickstarted the game on a high as they scored in the opening minute of the game. Haris Seferovic headed one past Rui Patricio following an inch-perfect cross by Silvan Widmer.
Portugal tried to pick themselves up following the early setback and came close to finding an equalizer. However, the Swiss remained resilient at the back and dealt with everything quite comfortably.
Danilo Pereira missed a good chance from a corner to equalize as he ended up heading it straight at the keeper. Goncalo Guedes came close to scoring in the second half as the 25-year-old latched onto a low-lying cross from Nuno Mendes.
Unfortunately, Jonas Omlin positioned himself well and closed down the space quite efficiently. The visitors scrambled in search of an equalizer till the very end but it just was not meant to be as Switzerland sealed all three points.
On that note, here's a look at the five biggest talking points from the game:
#5 Switzerland punish Portugal with their finesse
Switzerland scored the only goal of the game in the opening minute of the fixture. Switzerland attempted just one shot in the whole of the first half and that resulted in a goal for them. This early breakthrough made Portugal chase the game thereon.
Following their goal, the hosts were happy to sit back and absorb the pressure. They allowed Portugal to have the ball and keep at it while they defended with numbers at the back.
#4 Portugal lose their first Nations League fixture this campaign
Portugal's 1-0 loss against Switzerland was their first defeat of the campaign. The Portuguese started their campaign with a 1-1 draw against Spain but gained prominence within the group after defeating Switzerland and Czech Republic 4-0 and 2-0 respectively.
Things were looking smooth for the Portuguese national team but one round of fixtures has turned the whole scenario. Switzerland avenged their 4-0 loss earlier this month as they registered their first win of the campaign. Portugal's loss has opened up the race for advancement wide open.
#3 Jonas Omlin shines for Switzerland
Jonas Omlin was on fire against Portugal. The 28-year-old stood like a rock between the sticks and defied everything that came his way. The Montpellier goalkeeper made eight saves and recovered the ball 13 times throughout the game.
Omlin made some vital saves to deny Goncalo Guedes and Danilo Pereira. He read the game well and did what was necessary to keep his side ahead in the game. Omlin was one of the matchwinners for Switzerland and was clearly what stood between Portugal and all three points.
#2 Portugal miss Cristiano Ronaldo upfront
Portugal really missed their captain Cristiano Ronaldo against Switzerland. The Manchester United star was not included in the squad by Fernando Santos citing management reasons.
Ronaldo's absence was quite evident as Portugal struggled to cause commotion in the opposition's box. The visitors created a truck load of chances but missed their star man upfront who could have converted some of those. With Andre Silva higher up, Portugal did not have the same impact they would have hoped for.
#1 Delight for Spain
Spain defeated Czech Republic 2-0 and moved to the top of the table following Portugal's defeat to Switzerland. The Spaniards lead the pack with eight points whereas following them in second position is Portugal, who have seven points after four games.
Spain are the only team that is yet to lose a fixture in the group as they have won two and drawn two in the four games they have played so far. Santos' men will have to overcome the Spanish challenge in September if they are to advance further in the Nations League.