(CNN) -- In a sporting world where the big boys invariably grab all the glory, there is one competition where the romantic notion of the underdog toppling the giant sometimes becomes reality.
Not often, but regularly enough to keep seemingly hopeless dreams alive.
The English FA Cup is soccer's oldest knockout competition, and while it is often won by the greatest teams in the Premier League it is also the source of some of the greatest upset results.
"When you are a football club you dream of playing at Wembley, and today we saw the underdogs play with incredible bravery, incredible belief and they defied the odds again. That's the FA Cup," said Roberto Martinez after his Wigan Athletic team made their dream come true with a shock win against Manchester City on Saturday.
It was a result that ranked with Wimbledon's 1988 victory over Liverpool and Southampton's 1976 upset of Manchester United.
When Wigan lined up against City at Wembley, England's national stadium, there could not have been two more contrasting teams.
City -- funded by the oil money of its Abu Dhabi oil owners, winner of the Premier League last season and the FA Cup the one before that -- up against a Wigan side in its first final, having been a top-flight club for less than a decade.
Wigan's team cost £11 million ($17 million) in transfer fees -- City's squad had 11 players who had individually cost more than that.
Even before Sheikh Mansour bin Zayed Al Nahyan completed a reported $300 million takeover in 2008, City was already an established football name, even if its fortunes had faded since the 1960s and '70s.
Neighboring Wigan, on the other hand, was a non-league club until 1978 and only started moving up the divisions when entrepreneur Dave Whelan bought it in 1995.
Whelan was a former footballer who played in the FA Cup final for Blackburn in 1960, but badly broke his leg as his team lost, and never featured with a top team after that.
He subsequently made his money with a chain of grocery stores and then got into the sportswear business.
Now 76, he is an institution in the north-west town, having owned its rugby league team while also funding the football club's stadium -- which was first named after his business and is now known by his initials.
A sometimes controversial figure -- a backer of the Conservative party, he was the only leading football figure to call for a minute's silence to honor the late former Prime Minister Margaret Thatcher -- he has presided over a club that has battled to stay in the Premier League for the past few seasons.
"What an incredible story," Martinez said after an injury-time header from substitute Ben Watson earned a shock 1-0 victory over City, who had Pablo Zabaleta sent off for a second yellow card in the 85th minute.
"The chairman broke his leg in 1960 and today, finally, it's finished business for him."
Whelan was given special dispensation to lead out the team, as Wigan played its second major final -- having lost in the 2006 League Cup in Cardiff.
But now, although Martinez's team is guaranteed European football next season, Wigan's chances of staying in the top division hang by a thread with just two matches to play.
The Latics, as they are known, occupy the third and final relegation place and will have little time to celebrate the club's greatest day as Tuesday brings a trip to Champions League contenders Arsenal.
"We are going to get an incredible fight, incredible desire, to get the six points we've got left," Martinez said.
"But today is about today, today is about the FA Cup, today is about the victory and the trophy that we've won for Wigan Athletic. What an incredible story."
Martinez has been widely linked with a move to Everton following the imminent departure of David Moyes to replace Alex Ferguson at Manchester United, and was last year one of the candidates to take over at Liverpool before Brendan Rodgers got the job.
He is highly rated by Whelan, who has stood by the 39-year-old despite a seemingly constant Houdini act in keeping the club in the EPL, but it remains to be seen whether City's owners will show the same patience with their manager Roberto Mancini.
The Italian cut a forlorn figure at Wembley after the defeat left his side without a trophy this season, having been second best in the league as Manchester United won back the title.
Ferguson's surprise announcement this week that he is retiring after more than 26 years in charge took much of the focus off the FA Cup final, but the buildup to the match came with widespread rumors that Mancini will be replaced by former Real Madrid coach Manuel Pellegrini, who guided Malaga to the Champions League quarterfinals this season.
Pellegrini revealed on Saturday that he and several players would be leaving the Spanish club at the end of this season due to its money problems, which have resulted in a ban from future European competition under UEFA's financial fair play rules.
"Everyone would prefer to stay but unfortunately, the circumstances we are in don't allow that," the Chilean said.
Mancini helped City end a long wait for a trophy when he won the FA Cup in his first season in charge, but Saturday's defeat could be the end of the road for the 48-year-old after a difficult season in which he sold problematic striker Mario Balotelli -- who he had signed in 2010 from his former club Inter Milan -- and failed to make it past the group stage in the Champions League.
"This speculation is rubbish. If I said it's rubbish, it's rubbish ... speculation and rubbish," he angrily told UK match broadcaster ITV.
Mancini said he was "very sorry" for the 40,000 City fans who traveled to London for the match, which was played in pouring rain.
"They scored in the last minute so for us it was difficult. But we didn't play very well -- I don't know why," he told ESPN.
"It was a difficult season because our target was to win the Premier League, and we didn't win it.
But this can happen, it's impossible to win always.
"And after we had this chance to win another cup ... this moment is difficult."
Earlier Saturday, Frank Lampard became Chelsea's all-time leading scorer with both goals in a 2-1 victory over Aston Villa that all but ensured the London side will play in the Champions League next season.
The 34-year-old England midfielder has yet to be offered a new contract by the club, but he gave owner Roman Abramovich food for thought as he passed Bobby Tambling's longstanding mark of 202.
The win put third-placed Chelsea five points clear of Arsenal and six ahead of Tottenham, who both have a game in hand.
Villa took the lead through Christian Benteke's 19th league goal this season but the Belgian was sent off after the halftime break.
Chelsea had lost Ramires for a second booking before the break, but Lampard fired in a left-foot shot on the hour and finished from close range with nine minutes to play to take his tally to 15 this season in the EPL and 17 overall.
However, defender John Terry and midfielder Eden Hazard were taken off with injuries and are battling to be fit for Wednesday's Europa League final against Benfica.
Meanwhile, Manchester United midfielder Paul Scholes announced on Saturday that he will be retiring for the second time.
The 38-year-old quit in 2011 but was persuaded to return by Ferguson the following year.
He has not played since January, but Ferguson confirmed that the former England international will make his 498th EPL appearance on Sunday at home to Swansea.
"He will collect an unbelievable but well-deserved 11th Premier League medal," Ferguson said ahead of his own final home match at Old Trafford.