One figure has dominated this tournament for Brazil, and he is at the centre of the nation's attentions again. Neymar injured his knee and thigh in the penalty shoot-out victory over Chile and has not taken a full part in training since, instead jogging mournfully about with his right leg heavily strapped.
The team doctor, Jose Luis Runco, has insisted Neymar will be fit to play, but the question is how fit. Less newsworthy but just as significant may be the fact that the defensive midfielder Luiz Gustavo is suspended. Colombia have no new problems although the forward Carlos Bacca is still injured.
OVER-RELIANCE ON NEYMAR
Superbly as Neymar has borne the burden of his nation's expectations, he has had to. In Brazil's 3-1 win over Croatia in the opening game, it seemed at times that Neymar was taking too much responsibility, with the result that Brazil became predictable.
As the 1970 World Cup winner Tostao put it, Brazil had two strategies: give it to Neymar and give it to Neymar. Since then, as Oscar has faded, Hulk has toiled and Fred and Jo have looked clumsy and ineffective, it's come increasingly to seem that Neymar has been forced into becoming the focus of every attack - although cause and effect are difficult in this instance to disentangle.
Chile showed in the second half of their second-round game though, that if you stop Neymar you negate a lot of Brazil's sting. So far the Colombian holding midfield pair of Carlos Sanchez and Abel Aguilar have been quietly impressive, but this is by far their toughest test. That, of course, is assuming Brazil stick with their 4-2-3-1, but in training this week, Scolari has experimented with both a false nine and a back three. It may be that Neymar ends up punched higher, against the centre-backs.
EXPLOITING THE FLANKS
Defensively, the great weakness for Brazil so far has been behind their full-backs. Colombia seem ideally placed to take advantage, with Juan Cuadrado and Jackson Martinez (or Segundo Ibarbo if Pekerman goes back to the slightly less offensive approach he used in the opening game) adept at exploiting the spaces behind Dani Alves and Marcelo. Such a worry is it, that there is talk of the more defensively responsible Maicon returning to replace Alves.
At the same time, Colombia's full back pair of Juan Zuniga and Pablo Armero are keen to get forward, which will put the defensive capacity of Oscar and Hulk under scrutiny. If anything, the Colombian full-backs have rather more sense of defensive responsibility than the Brazilian pairing; if Colombia can dominate the flanks, it places even greater onus on the patched-up Neymar.
Colombia's formation has developed over the course of the tournament, but there seems little reason Jose Pekerman should switch from the same basic 4-2-3-1 he employed against Uruguay, with James Rodriguez taking up a classic number 10 position behind Teo Gutierrez. With five of Colombia's eleven goals so far, Rodriguez is the man Brazil have to stop, but the suspension to Luiz Gustavo will make it harder to do so.
Paulinho will probably return to partner Fernandinho at the back of midfield, but neither has the natural defensive instincts of the Wolfsburg anchor. A back three would provide an extra man as cover, but risks leaving just as much space for James to roam in.
THE FRAGILE CENTRE OF COLOMBIA'S DEFENCE
Colombia have been excellent going forward so far, but they are yet to play a giant who could test their defensive prowess. Mario Yepes is 38 and lacks pace and there have been times when the centre of that Colombian defence was exposed. Gervinho showed how uncomfortable they were when he ran at them, while there were a couple of moments towards the end of the first half against Uruguay when Diego Forlan and Edinson Cavani exposed them.
Yepes, you suspect, will be unfazed by Fred's aerial threat, but if Neymar can find space to run at the centre of the defence, he should prosper.
Before Chile met Brazil, much was made of their poor record against Brazil, and Colombia's isn't any better. They've met 25 times before, with Colombia winning only twice and in none of the 12 fixtures since 1991 when they won 2-0 in the Copa America. They have drawn their last four meetings, but there may still be a cultural cringe when it comes to finishing off the continent's traditional giants, particularly in their own back yard.
Brazil at 1.88 to win in normal time seems a little short, so it may be worth laying them. Equally, it's easy to imagine Cuadrado exploiting the space behind Marcelo, so back him to score at any time at 7.50
Bet on Brazil v Colombia now.