Argentina are favourites to come out on top of Wednesday's three-way race for South America's remaining World Cup place and a playoff berth.
When the Argentines meet Uruguay at the iconic Centenario in Montevideo needing a draw to secure their place at the 2010 finals they will, however, be no sure thing.
Ecuador, who visit qualified Chile, are also vying for one of the two places, including fifth which sends the occupants into a two-leg playoff against the team finishing fourth in the CONCACAF region.
Diego Maradona's Argentina team have disappointed as they stumble through the qualifiers, blindly hoping for miracles like Saturday's at River Plate's Monumental stadium in Buenos Aires.
Martin Palermo, 35 and recalled by his country after a 10-year international absence, scored two minutes into stoppage time to hand Argentina a 2-1 victory over Peru in a dramatic, rain-soaked finale.
Having dominated the first half and gone ahead through Gonzalo Higuain two minutes into the second, they allowed Peru to take the upper hand and conceded a 90th-minute equaliser.
MESSI MYSTERY
Maradona is criticised for his failure to mould a team out of a fine generation of Argentine players, including Lionel Messi who is a shadow of the Barcelona genius when he wears light blue and white.
Uruguay are the opposite to Argentina in that they are better on a good day than the sum of their parts.
A draw at high altitude in Quito against Ecuador on Saturday was going to keep them in with a slim chance and they paced themselves in a cautious performance until they fell behind to a Antonio Valencia goal.
They were level within a minute when Diego Forlan crossed for Luis Suarez to score and Forlan's injury-time penalty gave victory to Uruguay, who will likely be the less nervous team in Montevideo on Wednesday.
Ecuador had to win their home game knowing it would be difficult to beat a confident Chile side who secured their finals berth with an impressive 4-2 away win over Colombia, joining the already qualified Brazil and Paraguay.
Their coach Sixto Vizuete criticised Uruguay's tactics of slowing the pace, taking their time at dead-ball situations and committing niggling fouls.
"We lost to anti-football and with the referee's compliance in allowing (Uruguay) to play as they liked," Vizuete told reporters.
Uruguay will come up against an Argentina team who have shown little in the way of tactics, relying on the inspiration of individual players.
