A few American players arriving Tuesday at Mexico City's airport heard the chants from Mexican fans: "cinco, cinco, cinco" meaning "five, five, five." The good-natured gibes referred to Mexico's 5-0 victory over the U.S. just over two weeks ago in the Gold Cup final.
Aguirre is cautioning there'll be no repeat in Wednesday's crucial World Cup qualifier at the 105,000-seat Estadio Azteca. The U.S. is likely to field 11 different players from the "B" team it used at Giants Stadium.
"They'll use players, all new players," Aguirre said Tuesday. "We may field a similar team, but to score five goals - in quick succession like we did - is very improbable."
The United States has never won in Mexico, playing 23 times and losing 22 with a lone 0-0 draw in a 1997 qualifier. Mexico also holds a large edge in the overall series, but since 1990 the U.S. has lost only eight of 29 games with Mexico.
A U.S. victory would put it solidly on course to reach its sixth straight World Cup. A loss for Mexico could be a sharp blow for a team already struggling to get to South Africa.
"It's rare that you get a chance for redemption so quickly in sports," U.S. Soccer Federation president Sunil Gulati said Tuesday. "I think we're going to change history."
The U.S. must overcome several factors: an altitude of 7,400 feet; the smog and only two days of practice in Miami. Add to this the raucous fans and the deafening noise from blaring horns and beating drums.
The game is being played at 3 p.m. local time, not so much to avoid the heat - summer's are generally mild here - but to miss the showers that arrive regularly in the early evening during the rainy season.
Only four U.S. players have played at Azteca - forward Landon Donovan, and defenders Carlos Bocanegra, Oguchi Onyewu and Steve Cherundolo. Coach Bob Bradley is also making his first visit.
"My experience is that until you play in the game you don't fully understand what it's all about," Donovan said. "There's very specific things like the flight of the ball is different. A ball you think you might get your head on goes over your head."
Goalkeeper Tim Howard called playing at Azteca "almost a right of passage" for an American player.
Even with a loss, the U.S. would likely advance by winning its two remaining home games - against El Salvador on Sept. 5 at Sandy, Utah, and vs. Costa Rica on Oct. 14 at Washington D.C. It also plays away at Trinidad and Tobago and Honduras.
Mexico also has two home and two away games remaining, but a loss to the U.S. would be devastating. It was beaten 2-0 by the Americans in February at Columbus, Ohio. Two months later Mexico fired coach Sven-Goran Eriksson and replaced him with Aguirre.
Costa Rica leads the North and Central American and Caribbean region with 12 points, followed by the United States (10), Honduras (7), Mexico (6) El Salvador (5) and Trinidad and Tobago (2). The top three nations qualify, and the No. 4 team goes to a playoff against the No. 5 nation from South America for another berth.
In Wednesday's other qualifiers, Trinidad is home against El Salvador and Honduras is home against Costa Rica.
"When we play against them they take us up north, to the cold, where there are few Mexicans," Aguirre said. "Now we're back home with our fans, and 100 percent Mexican flags in the stands ... Our people, our passion and conditions that suit us."