Colombia and Uruguay, two teams in crisis, meet in a match neither can afford to lose while Argentina have a chance to regain the lead from Brazil in South America's World Cup qualifying competition on Sunday.
The Uruguayans have dropped to eighth place after home defeats against Venezuela and Peru and a coaching change in between -- with Jorge Fossati replacing eccentric Juan Ramon Carrasco -- has failed to stop the rot.
Leaders Brazil, who beat Argentina 3-1 on Wednesday with a hat-trick of penalties won and converted by Ronaldo, have a difficult match away to Chile, who go into the clash on the back of away wins in Venezuela and Bolivia.
Argentina,one point behind Brazil in second place, could go back to the top if they beat Paraguay in Buenos Aires and the world champions fail to win in Santiago.
Ecuador and Bolivia, who both pulled themselves back into the race with midweek wins at home, meet in Quito on Saturday and Peru complete the line-up when they host Venezuela in Lima on Sunday.
Although Brazil and Argentina look firm favourites to take two South American spots at the World Cup in Germany, this week's results have left the other places wide open.
Only four points separate Argentina, second with 11 points from six games, and eighth-placed Uruguay on seven.
Chile (10 points), Paraguay (10), Venezuela (nine), Peru (eight) and Ecuador (seven) are sandwiched in between. Bolivia (six) are ninth and Colombia (four) bring up the rear,
The top four teams qualify directly and the fifth plays off against the Oceania region winners for another place in Germany in 2006.
Brazil are the only unbeaten team with one third of the competition complete.
Colombia are again without injured striker Juan Pablo Angel and midfielders Freddy Grisales and Jorge Bolano for their game, which promises to be the most desperate of the weekend.
Uruguay, beaten 3-1 by Peru on Wednesday on Fossati's debut, are hoping playmaker Alvaro Recoba will have recovered from a training ground knock which left him out of the game in Montevideo.
Brazil are full of confidence for their game in Santiago but are always wary of visiting the National Stadium, which they have never found an easy venue and where they were beaten 3-0 on their last visit.
Chile strikers Marcelo Salas, still injured, and Mauricio Pinilla, who picked up a second yellow card for the way he celebrated his winning goal against Venezuela on Wednesday, are missing.
Argentina, and coach Marcelo Bielsa in particular, can expect a lukewarm reception from the public in Buenos Aires after their midweek defeat to Brazil.
Paraguay were also criticised for lack of ambition after losing 2-1 to Bolivia on Wednesday.
The Paraguayans will bring back several regular players from the trip to La Paz at 3,600 metres above sea level including central defender Julio Cesar Caceres.
They are also hoping workhorse midfielder Carlos Paredes will have recovered from a thigh strain.