A late goal from Xherdan Shaqiri saw Switzerland beat Serbia, who now face a final day showdown with Brazil.
The Swiss will qualify for the Last 16 if they beat Costa Rica, but the second group game is effectively now a play-off.
Torino’s Adem Ljajic dropped out after the first game, with Filip Kostic replacing him in the starting line-up.
Yann Sommer was called into action almost immediately, getting down to palm away Aleksandar Mitrovic’s header.
A late goal from Xherdan Shaqiri saw Switzerland beat Serbia, who now face a final day showdown with Brazil.
The Swiss will qualify for the Last 16 if they beat Costa Rica, but the second group game is effectively now a play-off.
Torino’s Adem Ljajic dropped out after the first game, with Filip Kostic replacing him in the starting line-up.
Yann Sommer was called into action almost immediately, getting down to palm away Aleksandar Mitrovic’s header.
It was a temporary reprieve however, as the Newcastle United striker soon opened the scoring.
Dusan Tadic cut back onto his left foot and sent in a looping cross, and Mitrovic beat Fabian Schar in the air to power a header home.
The striker’s confidence was such that he tried to score a header the edge of the box shortly thereafter, but the ball went safely over the bar.
Mitrovic’s next attempt was an overhead kick, but his effort went just over the crossbar.
Former Napoli midfielder Blerim Dzemaili had a great shooting opportunity just after the half hour mark, but he tried a cross and the chance was gone.
Switzerland replaced the ineffective former Fiorentina striker Haris Seferovic at half-time, and started the second period in command.
They got their reward on 53 minutes, thanks to a fantastic strike by Arsenal midfielder Granit Xhaka.
Xherdan Shaqiri’s shot was blocked by the Serbian defence, but the ball fell kindly for his teammate.
There was nothing lucky about the finish though, as Xhaka smashed the ball into the far corner on his left foot.
Mitrovic should have had a penalty on 65 minutes, but referee Felix Brych and the VAR officials somehow failed to spot he was being held by both Stephan Lichtsteiner and Schar.
Both teams knew they had to go for a win, with the Swiss having drawn their first game and Serbia still to face Brazil.
It made for an open and enthralling contest, with half-chances at either end.
It appeared that it would end in a draw, but Switzerland hit their opponents with a sucker punch at the end.
Serbia had committed men forward for a corner, which was headed away by Manuel Akanji.
In a lightning break, the ball found its way to Shaqiri, and Zoran Tosic was playing him onside, then tried to step up in vain.
The former Inter man kept his cool to slot the ball home and win the game for his country.
Switzerland will progress to the Last 16 if they beat Costa Rica in the third match, while Serbia and Brazil are effectively playing off for the other qualification spot.
Serbia 1-2 Switzerland
Mitrovic 5 (S) Xhaka 52 (Sw) Shaqiri 90 (Sw)
Serbia: Stojkovic; Ivanovic, Milenkovic, Tosic, Kolarov; Matic, Milivojevic (Radonjic, 81); Tadic, Milinkovic-Savic, Kostic (Ljajic, 64); Mitrovic
Switzerland: Sommer; Lichtsteiner, Schär, Akanji, Rodriguez; Haka, Behrami; Shaqiri, Dzemaili (Embolo, 73), Zuber (Drmic, 94); Seferovic (Garanovic, 46)