Switzerland, which had led Group B since the first round, will have to go through a playoff to try to make it to the tournament in Russian Federation.
But Portugal, who trail the Swiss by three points, can pip their opponents to first place with a victory as they have a vastly superior goal difference.
Switzerland had won all of its nine qualifiers until Tuesday's setback.
Joao Mario, Sommer and Djourou got into a tangle when attempting to get on the end of the cross, with the ball cruelly tricking over the line after contact from the former Arsenal man.
Silva added to the lead in the 57th with a shot into the open net after picking up a cross from the right by Bernardo Silva.
Nirmala says priority is on defence readiness
Chinese experts from various educational institutions have appreciated Sitharaman's initiative to advance goodwill. The Chinese soldiers in the area still have road construction equipment and other stores, they said.
It was then time for Cakir to make another debatable decision when a Cristiano Ronaldo shot inside the box bounced up off the hand of Ricardo Rodriguez with the defender seemingly knowing what he was doing.
However, Robert Lewandowski has since added another strike to his tally, and finished the campaign with 16 goals for Poland.
Switzerland never got going at the Stadium of Light and failed to materialise any decent chances, while Portugal dominated possession all too easily.
A draw would have been enough to take the Swiss through, but their 10-match winning run came to a disappointing end to mean a two-legged playoff next month to determine whether they will join their opponents in Russian Federation.
The game started slowly with Portugal dominating possession and Switzerland sitting back, looking to counter.
Who's already qualified for the 2018 World Cup? They cruised to a 4-0 victory over Cyprus in their final group game. A win would guarantee Argentina at least fifth place but a draw might be enough to take them into the top four depending on results elsewhere.