The time for truth has arrived for the men from Medellin.
Colombia's Atletico Nacional were the outstanding team in the group phase of the Copa Libertadores, winning their first five matches without conceding a single goal. But a cup competition is won by the team that comes good at the best time, not necessarily by the one that sprints out of the block with a flying start.
Perhaps Nacional have peaked too soon. In the first knockout round, their 4-2 aggregate win over Huracan of Argentina turned out to be a nervy affair. In the second leg, after seven clean sheets, they finally let in a couple of goals. Then in the first leg of the quarterfinal they went down 1-0 away to Rosario Central, superior Argentine opposition. The lack of away goals makes this a dangerous scoreline. If Central (usually a free scoring side) get one goal, Atletico Nacional will need three. Alarm bells are ringing in the Colombian camp.
In truth, they seemed to be on alert even before last week's encounter. Injury has robbed Nacional of Victor Ibarbo, who has been in wonderful form since ending an unsuccessful spell in the Premier League with Watford. Sufficiently versatile to play up front or in midfield, Ibarbo's strength on the ball made the game far easier for his teammates, especially the hugely promising Marlos Moreno, who began the Libertadores in such irresistible style, scoring in each of the first three games and winning a place in the Colombia national team squad. It's a remarkable rise for a 19-year-old who made his competitive first team debut as recently as last September.
Ibarbo is likely to be missing once again in Thursday's second leg. Can his teammates climb the mountain without him?
Last week coach Reinaldo Rueda appeared to doubt his team. Going into the competition, there was a doubt about the Nacional defence. Centre-back Oscar Murillo had been sold to Pachuca in Mexico. He is not especially classy, but he is quick; he has recently come into the senior Colombia side and performed impressively. Nacional's senior centre-back and captain is Alexis Henriquez: clever and talented but slow and getting slower. Alongside him, new man Davinson Sanchez is promising but raw.
Would the combination work? It certainly did for seven games, all of them with no goals conceded, but the doubts remained. Was it the case that the defence had been flattered by the weakness of Nacional's group opponents? Rueda seemed to lose confidence for the first leg against Rosario Central. Traditionally a fan of the conventional back four, he added Felipe Aguilar, a third centre-back, for the trip to Argentina.
The three centre-back formation was not a conspicuous success. Central scored early after a Sanchez error and could easily have won by a wider margin. The tactical switch also had implications for the rest of the team. With two wing-backs, two wingers and no Ibarbo to hold together the centre of the attack, Nacional badly lacked genuine attacking penetration. Marlos Moreno was left on the bench reflecting the suspicion that Rueda, a youth development specialist, feels that his young star has been affected by all the hype his early year performances have generated. Introduced for the last 15 minutes, Moreno was thrown on to a side without identifiable attacking structure, and he made little impression.
So what happens this Thursday? Playmaker Macnelly Torres wasn't selected for the first leg but made a claim to play in Medellin with two goals in the weekend draw with Patriotas. The good news was that he worked well with Moreno, who showed a welcome return to form.
Coach Rueda, then, has much to consider. There is a lot at stake in the second leg in the Atanasio Giradot stadium. If they fall by the wayside now, Atletico Nacional's blistering early form will be little more than a footnote in the story of the 2016 Copa Libertadores. But if they can mount a comeback then the Colombian champions, and Libertadores winners 27 years ago, will have a while to savour dreams of glory.
The semifinals are not played until July, after next month's Copa America. So if Atletico Nacional can overcome Rosario Central in front of their own fans in Medellin, then the Colombians will be able to spend almost two months partying like it's 1989.