What makes the underdog story so fascinating is that he or she is expected to go down, yet for whatever reasons defies the odds.
In Grand Slam tennis, underdogs don't just defy the odds once, twice or thrice.
They have defy the odds seven times before they can call themselves a Grand Slam champion.
Let's look at the 20 best tennis underdog stories in Grand Slam open era history.
The list isn't exhaustive, so if I've missed out, feel free to comment below.
Entering the 2002 French Open, Albert Costa hadn't won a tournament since the 1999 Generali Open, where he defeated Fernando Vicente 7-5, 6-2, 6-7, 7-6.
The only Grand Slam news Costa was making was negative, having effectively formed a anti-grass movement by boycotting Wimbledon.
Costa survived a mini-shock in the first round when a 15-year-old prodigy called Richard Gasquet took a set off the Spaniard.
Costa then beat three-time Roland Garros champion Gustavo Kuerten, two-time finalist Àlex Corretja and then compatriot Juan Carlos Ferrero in the final, who would go on to win the French Open a year later.
What's remarkable was that Venus Williams's first WTA tour final was the 1997 U.S. Open when she was only 17 years of age.
Williams played with a I don't give a damn attitude.
This was conveyed in her colourful image and her infamous collision with a more experienced Irina Spîrlea.
Ironically, Williams lost the final to someone even younger than her—the prodigious 16-year-old Martina Hingis.
Using Monica Seles as an inspiration, Marion Bartoli is one of the few players in professional tennis who still incorporates a double-handed forehand and backhand.
I remember watching Bartoli at the 2007 Australian Open and thinking she's a good professional but nothing else.
Her fourth-round victory over Jelena Janković was startling and then Bartoli followed it up with a monumental 1-6, 7-5, 6-1 semi-final victory over the undeniable favourite Justine Henin.
Bartoli cheekily said her inspiration came from James Bond actor Pierce Brosnan:
"I was focusing on Pierce Brosnan because he is so beautiful. I was just watching him. He was the only one—I said to myself, it's not possible I play so badly in front of him."
Although, the Frenchman was no match for Venus Williams in the final.
Er... Andy Murray's coach?
Yep, Darren Cahill was a modest tennis professional, but that run in the 1988 U.S. Open was epic.
A straight-sets victory over then three-time Grand Slam champion Boris Becker in the second round, who would win Flushing Meadows the next year.
Though Mats Wilander was too good in the semi-finals.
No-one could have envisioned qualifier and world No. 129 Jelena Dokić taking a set, let alone beating then world No. 1 and five-time Grand Slam champion Martina Hingis.
Dokić went on to humiliate Hingis 6-0, 6-2.
Before getting to the quarter-finals, Dokić also surprised ninth seed Mary Pierce.
In the quarter-finals, Dokić lost to an even bigger underdog...read on to find out who it was.
Christine O'Neil was the first unseeded woman in open era history to win a Grand Slam.
It would take another 30 years for an unseeded female to win a Grand Slam, which goes to show you how difficult the task is.
Nowadays, the O'Neil School of Tennis, an institution she started, is helping kids potentially accomplish what she did.
It was Richard Krajicek's first and only Grand Slam.
The Dutchman was like a light switch; he'd constantly turn on and off.
Pete Sampras felt the wrath of Krajicek when he was in the zone, and it was the American's only lost from 1993 to 2001.
Leading into the 2009 U.S. Open, Yanina Wickmayer had exited five of her last six Grand Slam tournaments in the first round.
Why would the U.S. Open be any different?
Then again, that year was pretty remarkable with Juan Martín del Potro etching his name in history and Kim Clijsters doing an Evonne Goolagong Cawley.
This was during the Steffi Graf era where she had won an astonishing 117 of her last 121 matches.
Arantxa Sánchez Vicario was talented, seeded seventh but in all fairness, she wouldn't trouble Graf.
Well, Graf choked, forfeiting a 5-3 lead in the decisive set and also gave away 71 cheap points.
Wimbledon's first-ever unseeded champion was just a 17-year-old school boy called Boris Becker.
He had turned professional a year before, but the idea that he'd run through the tournament and end up lofting the trophy at SW19 wasn't even contemplated.
Don't worry about four consecutive first-round exits; Angelique Kerber will find a way to make the semi-finals.
The classic underdog story was unseeded Gastón Gaudio going into the 2004 French Open 13-13.
Not only does he make the finals, he is down 0-6, 3-6 to Guillermo Coria, who at that time was one of the premier clay court players on the tour.
Coria threw away a two-set lead, two match points and countless breaks.
It was Gaudio’s first and last Grand Slam.
It was her second Grand Slam appearance; her first at Flushing Meadows ended in the first round.
Qualifier Alexandra Stevenson did well to beat 11th seed Julie Halard-Decugis, got past the tough Lisa Raymond, but surely Stevenson had no chance against Jelena Dokić who had just beaten then world No. 1 and five-time Grand Slam champion Martina Hingis.
Stevenson beat Dokić, but her miracle run ended there.
Martin Verkerk ended up losing more games than he won during his professional career.
It was an anomaly that he had reached the 2003 French Open final.
Guillermo Vilas was so intent on winning the Australian Open that he showed up six weeks prior to the event to practice.
Whilst John Marks was just a journeyman and defied form to reach the final.
Marks' next three Australian Opens all ended in the first round.
Gustavo Kuerten knocked off clay court maestro Thomas Muster, defending champion Yevgeny Kafelnikov and two-time French Open champion Sergi Bruguera.
This was an unknown Kuerten, a world No. 66 and was he even addressed as Guga back then?
Guga would win back-to-back Roland Garros titles in 2000 and 2001.
Mats Wilander was just an unseeded 17-year-old headed into the 1982 French Open.
By the 6th of June, he had beaten the second, third, fourth and fifth seed, and in the process had become a Grand Slam champion.
Goran IvaniŠević finally won Wimbledon, not as one of the most dangerous players on tour, but as a seemingly washed-up, past-his-prime veteran who had received a symbolic wild card into the event.
Eight months prior to Wimbledon, IvaniŠević made headlines when he was forced to default, having smashed every single racquet he had.
Mark Edmondson is the lowest ranked player to ever win a Grand Slam at No. 212.
He accomplished this by beating then seven-time Grand Slam and defending champion John Newcombe.
An unassuming 17-year-old Chinese-American Michael Chang, standing at just 5'7", had done well to reach the 1989 French Open fourth round against then three-time French Open winner Ivan Lendl.
But Lendl was expected to dish out a tennis lesson.
Chang had his back against the wall, and he would do something that became a part of tennis folklore.
He baited Lendl with balloon balls and even used the under-arm serve.
The normally ice-cold Lendl cracked under the pressure.
A week later, Chang became the youngest male Grand Slam winner ever by defeating Stefan Edberg 6-1, 3-6, 4-6, 6-4, 6-2.
A record that still stands.
Please also read The 20 Worst Temper Tantrums in Tennis History.