Carlos Tevez toiling with Boca Juniors in Copa Libertadores

With the group phase moving towards a close, the Copa Libertadores has reached a fascinating stage. The big question over the next few weeks is: who is going to crash out early?

Most of the teams have played four of their six group games and no-one has a 100 percent record. That competitive balance means the vast majority are somewhere in the middle, scrambling around to secure enough points to get them over the line and into the knockout stage, which takes place after the World Cup. Half of the teams go through, half go home. And with 16 former champions in the field of 32, that means some big names in the continent's history are doomed to an early exit.

Including, perhaps, the biggest name of them all. Buenos Aires giants Boca Juniors have won the title six times, four of them between 2000 and 2007. As reigning Argentine champions and league leaders this season, they went into the campaign as one of the leading favourites. But defeat on Wednesday would put an end to their hopes, and ruin the dream of Carlos Tevez to return to the club and carry them to title No.7.

Their group always looked intriguing. Palmeiras are a big Brazilian club with plenty of money behind them. And Junior of Barranquilla in Colombia are a dangerous side, capable of playing some exciting football. The other team, Alianza Lima, always looked like the makeweight. And Boca are paying the price for only drawing with them in the opening game in Lima. Those two dropped points might prove very costly.

Palmeiras have lived up to pre-tournament expectations, and are so far the only team to have guaranteed their place in the knockout round. Who accompanies them depends greatly on Wednesday's showdown in Colombia.

Junior started off with two defeats and changed their coach, bringing back Julio Comesana. They then registered home and away wins over Alianza, giving them six points, one more than Boca. So if they beat Boca on Wednesday night, the difference will be four points with one game to play -- meaning that Junior could not be caught.

Boca, meanwhile, have managed just two goals in their four games -- an indication of how disappointing they have been in 2018. The expectation was that the much-heralded return of Tevez would spark the attack to a new level. In fact, it would appear to have complicated matters. The veteran, 34, appears to lack the pace to operate as a genuine centre-forward. He has not dovetailed well with the side's Colombian playmaker, an ex-Junior figure, Edwin Cardona.

Perhaps the most important member of the side, ahead of Tevez, is holding midfielder Wilmar Barrios. He has suffered injury problems and missed last week's 2-0 defeat at home to Palmeiras. But he should be back to balance out the side against Junior.

Boca's opponents have problems of their own -- a fixture pile-up meant Junior played four times between April 22 and 29. Wednesday's match will go a long way towards deciding their fate in the Libertadores. And their destiny in the Colombian championship will be determined at the weekend in the last round of the regular season. Eight teams go into the play-offs. Junior currently lie eighth.

This, then, is a crunch week for both teams. And if the stakes are high, then so will be the temperature. Near the Caribbean coast, Barranquilla is a city of sweltering tropical heat. Conditions will be very different for Boca from their last match, a domestic league game suspended at the weekend as a result of driving winterish rain. Perhaps the change of scenery will inspire a change of fortunes for Tevez & Co.