Momentum may be the most important factor in the World Cup.
Just ask the Italians. The defending champions have over the years perfected the art of generating momentum, winning the titles in 1982 and 2006 by gaining speed as the tournaments progressed.
Now the U.S. has it after a sensational 1-0 win over Algeria that sent the team into the second round of the World Cup on a delirious high.
With an injury-time tap-in from Landon Donovan, the U.S. story changed in a sensational flash.
An earlier blown call -- a Clint Dempsey first-half goal wrongly disallowed for offside that had threatened to send the U.S. out of the World Cup on a sour note of repeated refereeing injustice -- was instantly forgotten.
Instead the U.S., which has looked tepid at times in the opening matches, moves into the second round after having played its best soccer of the tournament during the latter stages of the game against Algeria.
Suddenly what looked like turning into a winless World Cup for the U.S. has the team undefeated and winners of Group C, ahead of England.
If the Americans had finished second in the group, as most people had predicted, they would have been up against Germany in the second round.
This being a World Cup full of twists and turns, however, the U.S. will now line up against what is likely to be the only remaining team from Africa, Ghana, which scraped through despite a 1-0 loss to Germany thanks to Australia's win over favored Serbia.
A U.S. win against Ghana would see the Americans face either Uruguay or South Korea in a quarterfinal.
While Uruguay, in particular, has impressed with star striker Diego Forlan in top form, it looks on paper like the U.S. has a kinder route forward than teams elsewhere on the schedule.
It would not, for example, face heavyweights like Brazil or Spain until a possible semifinal.
But we're getting way ahead of ourselves.
First the U.S. will have to get past a Ghanaian team that has established itself as Africa's hope with an entertaining style of soccer built on quick and short passing.
This will be a re-match from four years ago.
Then, it was Ghana that eliminated the U.S. the Vup by beating the Americans 2-1. The Africans went on to the second round in their first-ever World Cup, where they were beaten by Brazil 3-0.
The Black Stars, as the Ghanaian team is called, are a much-changed side from the 2006 line-up.
Anchored by the smooth Anthony Annan, the young midfield has impressed so far in the Cup and doesn't seem to be missing injured superstar Michael Essien, the Chelsea midfielder.
But like other African teams in this tournament, Ghana has had a horrid time in front of goal, with only two goals scored and both of them on penalties by lone striker Asamoah Gyan.
Against Germany, Ghana wasted five or six golden opportunities to score against a surprisingly shaky German defense.
The U.S., meanwhile, has its own problems up front.
Against Algeria, striker Jozy Altidore also missed several chances to put the U.S. ahead.
Much like England's Emile Heskey, Altidore is a work horse who would benefit from playing next to a goal-poaching striker, something the U.S. sorely lacks.
He did, however, play an important role in the late-winning goal by putting in the cross that Clint Dempsey shot at Algerian keeper Rais Bolhi. It was the rebound from that shot that Donovan scored on.
It's clear that midfielder Donovan is as close to a match winner as the U.S. has. So far, none of the U.S. goals have come from the team's strikers.
The team's greatest asset, however, continues to be its great fighting spirit and never-say-die attitude, something that is rubbing off on the growing legion of U.S. fans who turned the Loftus Versfeld Stadium in Pretoria into a sea of blue, red and white.
After the game, U.S. Coach Bob Bradley spoke of a "special moment" when the U.S. team arrived at the stadium to be greeted by scores of U.S. fans wishing the team good luck.
"We're not done yet," said Donovan, who fought to keep tears back in a post-game interview.
He knows his team has momentum on its side.
And, as the Italians know, once that is generated, it will take a great force to stop it.