VANCOUVER, British Columbia (AP) -- Heather Mitts remembers the feeling walking off the field in Cancun, having been a part of the first and only loss the U.S. women's soccer team has ever suffered in a qualifying match for the World Cup or Olympics.

"It was awful," Mitts said. "It was obviously for us a real wakeup call. We definitely weren't prepared. We weren't prepared, and they came out and they played great against us."

Final score: Mexico 2, United States 1. It was Nov. 5, 2010. Mexico had punched its ticket to the World Cup. The Americans would have to play three more games to get there.

The opportunity for payback has arrived. The U.S. plays Mexico on Tuesday for first place in their group in the CONCACAF qualifying tournament for the London Olympics.

"That's obviously the game that's been marked on our calendars this entire tournament," forward Abby Wambach said.

And, yes, the teams have met once since the game that many consider to be among the biggest upsets in soccer history, but it was an exhibition in New Jersey last June, a warmup for the World Cup won 1-0 by the U.S.

That hardly counted as revenge.

"No. Absolutely not," Mitts said. "That was a friendly. This is Olympic qualifying. It doesn't matter if we're playing Mexico or not; we still have to win these games to get to the next step. I think it does add to it that we are playing Mexico - and the revenge factor does help."

Beyond having a score to settle, the game is a vital one. The region only gets to send two teams to London, and four remain in the hunt. The winner of the U.S.-Mexico game was expected to draw an easier match against Costa Rica in the do-or-die semifinals, while the loser was projected to face off against the formidable Canadians.

Coach Pia Sundhage and her players spent much time contemplating what went wrong in Cancun 14 months ago. Sure, the Mexicans had home-field advantage - the rowdy crowd spent the game chanting and throwing cans, bottles, paper and other objects toward the field - but it's a brutal fact that the Americans were so used to winning that complacency had settled in.

"I definitely think taking a team for granted - and maybe thinking we were better than what we were - had a lot to do with it," forward Lauren Cheney said.

Cheney also said many of her a teammates were simply exhausted. The Cancun tournament, and the camp that preceded it, had come at the end of the long Women's Professional Soccer league season.

Sundhage takes the blame for that. She said the team wasn't sharp during the entire tournament.

"When I think back, I made a mistake having them together too long," Sundhage said. "I learned my lesson."

For the Olympic qualifying, the team had a shorter camp in California before arriving in Vancouver. It's hard to judge the results thus far: The Americans have won by scores of 14-0 and 13-0, but their opponents were so overmatched it wouldn't have mattered much how the U.S. prepared. The most helpful result of the blowouts is an overwhelming goal differential that means a draw against Mexico will be enough to win the group.

Mexico also has been cruising through the tournament, winning 5-0 and 7-0 against the same teams the Americans have played. The lopsided scores have allowed both teams to rest key players to keep them fresh for Tuesday's showdown.

While the Americans cite the loss in Cancun as more evidence of a growing parity in women's soccer, Mexico coach Leonardo Cuellar said his country has far to go to catch up with its counterparts to the north.

"They're obviously the best in the world," Cuellar said. "You see the U.S. and Canada, they basically have national teams that if they're not living together, they are dedicated to a national team. For us we still have players that go to school, go to work. We're at a different level, so it's a big challenge for us."

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