The long-running battle for footballing supremacy between neighbours Mexico and the United States is thrust under the global spotlight on Monday when they meet for a place in the World Cup quarter-finals.
Almost 70 years of intense, often fractious, rivalry has seen the sides meet 46 times, many of those in World Cup qualifiers, but never before in the finals.
Now, with Germany awaiting the winners, it really is time to see who are the kings of the CONCACAF region.
"It's going to be a battle," said U.S. midfielder Landon Donovan, who described relations between the two countries as "definitely not friendly".
"We know we can beat them and they know they can beat us."
The United States, who lost all three first round games four years ago, are bidding to reach the last eight for the first time since the modern format was introduced.
They reached the semi-finals in the first World Cup in 1930 with just two wins, before losing 6-1 to Argentina.
They got through to this year's second round in somewhat bumpy fashion, beating Portugal 3-2, drawing 1-1 with South Korea and then losing 3-1 to already-eliminated Poland.
It was a performance that sums up their whole game -- inconsistent. If they play as they did in the first half against Portugal, when they raced into a 3-0 lead, they are capable of beating not only Mexico but many of those left in the tournament.
If they perform as they did in the early stages against the Poles, then their World Cup will end at around 5.30 p.m. local time (0830 GMT) on Monday.
The Americans are hoping their shocking start against Poland, when they trailed 2-0 after five minutes, will galvanise the side back to their best.
"Maybe it was a good wake-up call for us," said goalkeeper Brad Friedel, who saved his second penalty of the tournament late in Friday's match. "If we would have won we may have gone into the Mexico game a bit cocky."
Coach Bruce Arena said: "We will re-group, we'll be fine."
Arena said he had a great respect for Mexico, who the United States played twice in qualifying, with a win apiece, and then beat 1-0 in their last meeting in April.
"The rivalry is immaterial," he said. "You need to talk about Mexico in the World Cup...they have been one of the top teams here.
"We know their team well, they know us well and it's going to be a good game."
Arena faces a couple of selection quandaries as centre back Jeff Agoos will miss the game with a calf injury, while right back Frankie Hejduk is suspended after picking up his second yellow card against Poland.
Mexico, appearing in their 12th World Cup, are bidding to reach the quarter-finals for the first time outside their own country, having got there on home soil in 1970 and 1986.
Judging by their first round performances, they look well-equipped to do so and, for once, it seems the players might actually believe it.
"We are playing some great football at the moment and we are confident we can get through," goalkeeper Oscar Perez said on Saturday.
Striker Cuauhtemoc Blanco added: "We have come here playing well and will try to continue that by attacking from the first minute."
Mexico beat Ecuador and Croatia in their group and got the better of Italy before drawing 1-1 with their brand of quick inter-passing and clever lay-offs that is very difficult to defend against when it goes well.
Coach Javier Aguirre said on Saturday he has no injury, fitness or suspension worries and looks set to start with the same team that played against Italy.
Mexico (4-4-2): 1-Oscar Perez; 7-Ramon Morales, 5-Manuel Vidrio, 4-Rafael Marquez, 11-Braulio Luna; 21-Jesus Arellano, 16-Salvador Carmona, 6-Gerardo Torrado, 18-Johan Rodriguez; 10-Cuauhtemoc Blanco, 9-Jared Borgetti.
United States (4-4-2): 1-Brad Friedel; 23-Eddie Pope, 22-Tony Sanneh, 4-Pablo Mastroeni, 6-David Regis; 5-John O'Brien, 8-Earnie Stewart, 10-Claudio Reyna, 21-Landon Donovan; 11-Clint Mathis, 20-Brian McBride.
Match referee: Vitor Melo Pereira (Portugal)
Linesmen: Carlos Matos (Portugal), Egon Bereuter (Austria).