J ulio Cesar could have been speaking for all of the Copa America's high-profile players.

“We cannot relax,” the goalkeeper said wearily after Brazil’s 4-2 victory over Ecuador secured their place in the quarter-finals. Argentina and Uruguay also had to rely on winning their final matches to qualify from the group stages, and the tournament’s opening two weeks have been characterised by a general malaise.

The individual stars and the established nations have yet to live up to expectations, and the boos that greeted Argentina as they left the field following a 0-0 draw with Colombia in their second group game were typical of the sense of disenchantment.

As hosts, Argentina face a greater pressure to perform, but Lionel Messi’s poor displays in the opening two games seemed to signal an existential crisis that was affecting the whole squad.

It took a drastic change to alter their mood. Sergio Batista, the coach, ditched the 4-3-3 formation — based on Barcelona’s tactics — and dropped Carlos Tevez, Ezequiel Lavezzi, Ever Banega and Esteban Cambiasso for the final group game against Costa Rica. Of the four players who came into the starting line-up, Sergio Aguero scored twice and Angel di Maria added the third.

It took a change of shape and personnel to bring some life to Brazil’s forward line, too, and Neymar responded by eventually finding something of the form that has established the flamboyant teenager as the next great wonderkid of the game. He scored twice against Ecuador, as did Alexandre Pato of AC Milan, and the hope for the tournament is that the major sides are now building momentum.

But even glimpses of aplomb -- Radamel Falcao, the Colombian striker, is the Copa’s top scorer and his finishing has been brutally clinical — are not enough to counter the growing impression that international football can no longer compete with the glamour and intrigue of the leading domestic and European competitions.

The likes of Alexis Sanchez, Messi, Lavezzi and Diego Forlan have all been leading players for club sides in Serie A and La Liga in recent seasons, but have yet to display the same accomplishment at this regional tournament.

Last summer’s World Cup similarly did not deliver the kind of imperious moments that last in the memories of a generation of football supporters, as players succumbed to fatigue and, perhaps, a diminishment of their ability to keep delivering the very best of themselves without respite.

If the Copa America has stirred again this doubt about the capacity of international football to captivate as it once did, the rise of the underdog has at least generated some fascination.

Venezuela and Peru tend to be written off as fodder to the leading nations in South America, yet both have qualified for the quarter-finals, while Colombia have been the most impressive side in the competition so far. What distinguishes the latter — who have won the tournament only once — is that they are not so reliant on a sole, iconic player to succeed, but instead have kept faith in their team ethic.

Falcao provides the threat up front, but it is their 4-1-4-1 formation, solid but still allowing an adventurous nature to be expressed, that has enabled them to perform with such assurance so far.

Hernan Gomez’s side are also facing Peru on Saturday and should be strong enough to reach the semi-finals; as should Chile, who face Venezuela the following day. The other quarter-finals that are more difficult to call. Brazil could only draw with Paraguay and the Venezuelans in the group, but will feel that they have regathered their poise.

Argentina and Uruguay, who play tomorrow, are dependent on their attacking players, since their defensive units are not as accomplished. Uruguay, in particular, have struggled at the back and there is a feeling that the team has maybe run its course.

For the tournament organisers, the hope is that Argentina progress, to keep interest high among the home fans. Messi was more influential against Costa Rica, and the combinations he managed with Di Maria and Gonzalo Higuain were fluent and dangerous.

There is so much resting on Messi’s narrow shoulders that he might be forgiven for feeling isolated by his fame, particularly in a side that is not as well-balanced as Barcelona (where he is assisted by Xavi, Andres Iniesta, David Villa, Pedro and Sergio Busquets), but he seemed stung by the criticism that followed the opening two games and will consider his performance against Costa Rica as a riposte.

Brazil have won four of the last five Copas and might yet establish themselves as the pre-eminent side. So far the tournament has been unable to live up to the anticipation of drama and artistry, but there is still time for hope to prevail.