Welcome to ESPN's fan vote, where you, the reader and sports fan, will decide which individual or team has been the most dominant in the 21st century.
In our first semi-final, the fastest man on earth, Usain Bolt edged past Virat Kohli's India to become the first finalist. In our second semi-final we have the King of Clay Rafael Nadal up against one of the greatest Olympians of all time, Michael Phelps.
(Please vote in the poll at the bottom of this page to decide the winner.)
Rafael Nadal at the French Open (2005-present)
Imagine winning a Grand Slam on debut. Imagine preventing Roger Federer, one of the greatest players ever, from completing a Career Grand Slam (winning all four majors at least once) not once, not twice, but four times in succession. Imagine doing that to Novak Djokovic, another GOAT contender, three years in a row.
Imagine winning that Grand Slam 12 out of the 15 times you've played it, racking up a ridiculous 93-2 win-loss record in the process. Imagine doing all this while facing the pressure of expectations so heavy that anything less than winning that tournament is taken to mean you are finished.
That is Rafael Nadal's record at the French Open.
Michael Phelps at the Olympics (2004-2016)
For 12 years, Michael Phelps dominated the swimming pool. He was probably, in that time, the most dominant individual athlete across sport. Sure, he lost races; he famously lost his last individual Olympic race to Singapore's Joseph Schooling, who looked up to Phelps and had a photo taken with the American when he was 13. But from 2004-16, every time he entered the pool, he was the swimmer to beat. And in a sport with a relatively short shelf life, that's a long time to be so dominant.
No wonder when he retired, after the Rio Olympics, he had these all-time records to his name: Most Olympic medals; most Olympic gold medals; most gold medals at a single Games; most swimming world records. The list goes on. His standout year was 2008, when he won every event, individual or team, he competed in at the Beijing Olympics; and his standout event was the 200m individual medley, which he won in four consecutive Olympics.
(If the poll doesn't load, click here to try again. The poll will close at 9:30 AM IST on Thursday July 16)