The Lionel Messi show is coming to this southern Brazilian city, along with hordes of the Argentina striker's loyal fans.
Porto Alegre is close to the Argentine border, and thousands have already made the crossing into Brazil, many sleeping in buses and vans ahead of Wednesday's game against Nigeria. Local media say more than 50,000 are expected, though less than half will have tickets, in what could be a test for security authorities.
As predicted in the run-up to the tournament, Messi has been the key to success for Argentina, which has already qualified for the second round. Currently top of Group F after two scrappy wins, it will stay there if it gets at least a point against Nigeria.
A draw would also suit the Nigerians, who would seal second place in the group and their first appearance in the knockout stages since 1998. They could also lose and still progress if Iran fails to beat Bosnia-Herzegovina in a match being played at the same time.
Argentina will be looking for a better team performance in front of its fans, who have had little to cheer about so far — apart from Messi. The 26-year-old Barcelona star scored a second-half goal against Bosnia-Herzegovina in an opening 2-1 victory, and popped up in added time to curl in a left-foot shot from outside the penalty area for the only goal of the game against Iran.
Nigeria arrived in Brazil as the reigning African champions but underwhelmed at last year's Confederation Cup, where it lost to Uruguay and Spain after an easy win over Tahiti. The team wasn't tested much in qualification for the World Cup.
With the likes of Chelsea's John Obi Mikel and Liverpool's Victor Moses in the squad, Nigeria is where most people expected it to be in Group F, in second place behind Argentina. After a 0-0 draw with Iran 0-0, Nigeria played better in a 1-0 victory over Bosnia-Herzegovina, courtesy of a first-half goal by Stoke City striker Peter Odemwingie.
The group remains tight, and one set of results on Wednesday would see second place decided by the drawing of lots by the FIFA organizing committee. If Nigeria loses 1-0 and Iran wins 1-0, both teams would have the same goal difference and number of goals scored, and could not be separated by their head-to-head result.