Can Independiente del Valle gatecrash Boca, Sao Paulo at Copa Libertadores?

After a 43 day pause for the Copa Centenario, South America's premier club competition returns this week with four teams left standing as the semifinals of the Copa Libertadores get underway.

Four different countries are represented in the last four. Brazil's Sao Paulo play host to Atletico Nacional of Colombia in Wednesday's first leg. Then, 24 hours later, Boca Juniors of Argentina visit the fairy tale side, Ecuador's Independiente del Valle. The first three clubs share 10 Libertadores titles, while 10 years ago Independiente were playing in their country's third division. A little club from the outskirts of the capital of Quito, their rise has been based on splendid youth development work and a sense of continuity which has given them a strength and team spirit to carry them through round after round.

It has always been tight for the upstarts. In 12 games they have scored just 14 goals, while conceding only 10. The margin of victory has seldom been comfortable, and they have needed to produce some stubborn rearguard actions away from home to keep scraping through. At home, though, they are unbeaten, with a record of five wins and one draw. The altitude of Quito, some 2,800 metres above sea level, works in their favour, and they will look to press it home on Thursday against Boca.

The Buenos Aires giants, though, are the only unbeaten team left in the competition. They have climbed higher than Quito in this campaign, to 3,600 metres above sea level in La Paz in Bolivia, where a last-gasp free kick earned them a draw against Bolivar. They have also made an interesting addition to their squad in striker Dario Benedetto, fresh from a successful spell with America in Mexico City. Altitude will not be a problem for him, and Boca hope that he will dovetail well with Carlos Tevez, their leading scorer in the campaign with five goals.

With six titles and the glamour of being one of the most popular clubs in the continent, Boca against little Independiente del Valle is a match that contains all of the charm of the Libertadores.

The other semifinal, though, sheds light on the competition's organisational deficiencies. That seven-week pause has interfered with the integrity of the clash between Sao Paulo and Atletico Nacional. The Colombians were the sensation of the group phase of this year's tournament, but that team no longer exists. In the two semester structure that many South American countries follow, the contracts of key players have come to an end.

The most important member of the side in the first few months of the year was Victor Ibarbo, an international midfielder whose versatility and strength on the ball made him the centrepiece of the team. His loan spell has ended and he has moved on, along with fellow international holding midfielder Alexander Mejia, promising centre-back Davison Sanchez and winger Jonathan Copete, the team's joint top scorer in the current campaign with three goals. Replacements have been acquired, but there has been little chance for coach Reinaldo Rueda to bed them in because the Colombian championship paused during the Copa Centenario.

There was no break in action in Brazil, though, so Sao Paulo go into the first leg battle hardened and ready. Even in the absence of injured playmaker Paulo Henrique Ganso, they are favourites to build up a first leg lead over their Colombian rivals.