Which South American giant will miss out on the World Cup?

South America's World Cup qualification campaign is now in the home straight, and two of the riders have already crossed the line.

With four rounds still to play, Brazil and Argentina have both booked their place in Qatar -- which is a partial explanation for the absence of Neymar and Lionel Messi from the squad lists for this penultimate double header.

Brazil were even thinking of playing the final rounds with an under-23 team while they fixed up friendlies against European opposition for the senior side. FIFA quite correctly knocked the idea back. There might be little riding on the last rounds for Brazil, but not for all the other teams battling for the two and a half slots (the team finishing fifth goes into a intercontinental playoff) still on offer from South America. Indeed, there is no such thing as an inconsequential match in this week's set of fixtures. All five matches have a direct influence on who goes to Qatar and who stays home.

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Ecuador have solid grounds to believe that they will be in the former group. They lie third in the CONMEBOL table with a six-point cushion over the chasing pack and a massive advantage in goal difference. Barring a disaster and a mathematical miracle, they will go into the final two rounds still in third place.

Even so, there are concerns gnawing away at the Ecuadorian mind. They pick up most of their points at home,and their only remaining home games are against the big two -- Argentina in March and Brazil this Thursday. And a surge in COVID-19 cases means that, barring a late change of mind, they will have no fans in the stadium in Quito roaring them on.

For Brazil coach Tite this is an evocative fixture. His first game in charge of the Selecao was a crunch qualifier in Quito almost five and a half years ago. Brazil were in dire trouble at the time, and struggled to hold the Ecuador attack. Well into the second half Tite would have been happy with a goalless draw. Instead, everything went right in the closing stages and Brazil won 3-0, gaining confidence to turn the rest of the qualification campaign into a victory parade, just as this one has been.

The only games Brazil have failed to win this time have been the last two away matches, both drawn. Without Neymar, there is another chance to have a look at the quartet of Vinicius Junior, Lucas Paqueta, Matheus Cunha and Raphinha, who formed an exciting combination in the last game against Argentina.

The man to watch for Ecuador is centre-back Felix Torres. Since his introduction in September the team have conceded just three goals in eight games, and none in the last three. This will be his biggest test so far, and another clean sheet ensures that Ecuador pick up at least one point, taking them closer still to Qatar.

The two teams behind them are Colombia and Peru, who meet in Barranquilla on Friday. They are separated by goal difference, leaving Colombia in fourth, the last automatic slot, and Peru in the playoff position.

This already represents a triumph for Peru, who were bottom of the table when the action resumed in September. Just as he did with the 2016 Copa Centenario, coach Ricardo Gareca used the 2021 Copa America to regroup and rally. Peruvian football is not giving him many new players to work with, but Gareca is working wonders. His team now have to take on the fierce afternoon heat of Barranquilla, and a Colombian side who, astonishingly, have gone five games without scoring. In 11 qualifiers under coach Reinaldo Rueda, Colombia have suffered a single defeat. But there have only been two wins, starting with a 3-0 win in Peru last June. The lack of goals appears to have become a psychological trauma -- eased this time, they hope, by the return of James Rodriguez.

A point behind Colombia and Peru are Chile, who hauled themselves back into contention with three wins in their last four games. They now host Argentina, and for the first time ever Chile will stage a competitive game outside Santiago.

This match has been moved to Calama, in Chile's northern desert. The climate is inhospitable. As well as altitude, at this time of year there are wild temperature fluctuations, from searing summer heat in the daytime to near freezing at night. The switch smacks of desperation, and even some of the Chilean players are unconvinced that it will hand them much of an advantage. Moreover, Arturo Vidal is suspended and Chile have not won a match in this campaign when he has been missing.

Argentina, of course, are without Messi. Perhaps opportunity could knock one more time for the enigmatic Pablo Dybala? And key centre-back Cristian Romero is also missing, giving the Chile strike force of Alexis Sanchez and Ben Brereton Diaz hope that Argentina's record of six consecutive clean sheets can be brought to an end.

Level on points with Chile are Uruguay, who begin the reign of coach Diego Alonso with a trip to Paraguay.

The Paraguayans still have a mathematical chance of sneaking into the playoff place, but it would take a miracle. So far they have only beaten Venezuela; to stand a chance they would have to win all four matches, including away to Brazil, who have never lost a World Cup qualifier at home.

This game, then, is all about Alonso and Uruguay. What changes will the new coach make? He has kept faith with the old guard of predecessor Oscar Washington Tabarez, but he has also made a point of calling up a couple of players who could not find a place in the old regime -- such as keeper Sebastian Sosa and striker Nico Lopez. Will Alonso stick with the Luis Suarez-Edinson Cavani partnership up front? Uruguay have often looked more fluid lately when it has been a case of one or the other. And at centre-back? Alonso is surely praying for the health and fitness of Jose Maria Gimenez, and trusting in the progress of Barcelona's Ronald Araujo. Is there still a place for Diego Godin? In the middle of a back three, perhaps? Uruguay's new coach is in the deep end, having to take instant decisions about both the personnel and the shape of his side.

A point behind Chile and Uruguay are Bolivia, swaggering with confidence after three recent home wins and some interesting experiments in recent friendlies. At the extreme altitude of La Paz they are feared, but winning their remaining two home games will not be enough. They need an away victory, and on Friday they travel to face bottom of the table Venezuela.

This campaign has been a prolonged disaster for Venezuela, who had been dreaming of making their World Cup debut in Qatar. They now start a new era under another new coach -- the vastly respected and experienced Argentine Jose Pekerman. For them, this match represents the start of the road towards the 2026 World Cup. For Bolivia it is a game they need to win to have a chance of going to Qatar this year -- it may well be the most important Venezuela-Bolivia match in history.