If there was ever was any doubt, today surely showed that Lin Dan is the greatest badminton player we have ever seen.
The Olympic champion from China won his fifth world title after first coming from a game down and then overturning a 10-6 final game deficit to force his great rival, and good friend, Lee Chong Wei to retire at 20-17 down.
Chong Wei needed treatment for severe cramp brought on by dehydration when trailing 19-16 but after winning the next point he dropped to the floor in the middle of the following rally.
Lin Dan went over to his opponent's side of the court to speak to him, but the umpire called an end to the contest and Lee left the arena on a stretcher and was taken to hospital, missing the medal ceremony. It brought back memories of the marathon 1997 final in Glasgow when Peter Rasmussen overhauled Sun Jun after the Chinese star suffered cramp in the third game of a 124-minute battle.
It was a sad end to the contest with Lin Dan winning 16-21 21-13 20-17 but how lucky we are to see such a brilliant champion and how lucky to enjoy such special rivalry between these two giants of the modern game.
But how unlucky for Chong Wei that the Malaysian is playing in the same era as an opponent who has now beaten him at the 2011 worlds, 2012 Olympic and 2013 world finals.
The Malaysian has been trying to win this world title since his debut year in 2005. Then he won bronze behind Taufik Hidayat's gold and Lin Dan's silver. But he surely never imagined that eight years later his two silvers today and in 2011 would be the closest he may ever get as he will be 31 in October when Lin Dan also hits 30.
Today's final was another epic, lasting 93 minutes to make it the longest match of the Championships.
But what makes it more amazing is that Lin Dan has retained his crown despite taking virtually a year off since his Olympic triumph. His only matches before this week was a farewell contest to mark Peter Gade's retirement at the Copenhagen Masters in late December and three tournament wins at the Asian championships in April.
He even needed a wild card from the BWF to compete in these World Championships. Even so, he didn't drop a game this week until Chong Wei took the opener in the final.
Despite Lin Dan's triumph today's finals saw the end, for the moment, of China's World Championships domination. The nation who won all five titles at the London 2012 Olympics had done the clean sweep at the 2010 world championships in Paris and again at London 2011.
And although they began finals day in contention for four titles, they ended up with just the two.
Wang Xiaoli and Yu Yang retained their women's doubles title but 2010 winner Ma Jin and partner Xu Chen lost their mixed doubles final to Tontowi Ahmad and Liliyana Natsir of Indonesia with Natsir becoming world champion for the third time after victories in 2005 and 2007 and silver and bronze in 2009 and 2011.
The women's singles event they have won eight times since 2001 slipped from their grasp as Yonex All England runner-up Ratchanok Intanon became Thailand's first gold medallist and, at 18, badminton's youngest world champion when she defeated China's top seed Li Xuerui 22-20 18-21 21-14.
With the semi-final defeat of four-times world men's doubles champions Cai Yun and Fu Haifeng, this was the one title China could not win even before finals day began.
But Denmark's hopes of lifting gold for Europe were dashed when Mohammad Ahsan and Hendra Setiawan beat them in straight games to give Indonesia two golds.
That left Denmark - and Europe - with just a men's doubles silver and a women's doubles bronze for Christinna Pedersen and Kamilla Rytter Juhl.
The 2014 World Championships are in Denmark next August.
Lin Dan (Chn) bt (1) Lee Chong Wei (Mas) 16-21 21-13 20-17 retired (93mins)
Gold: Lin Dan (Chn); Silver: Lee Chong (Mas); Bronze: Du Pengyu (Chn), Tien Minh Nguyen (Vie)
(4) Ratchanok Intanon (Tha) bt (1) Li Xuerui (Chn) 22-20 18-21 21-14 (65m)
Gold: Ratchanok Intanon (Tha); Silver: Li Xuerui (Chn); Bronze: Yeon Ju Bae (Kor), P. V. Sindhu (Ind)
(6) Mohammad Ahsan & Hendra Setiawan (Ina) bt (3) Matthias Boe & Carsten Mogensen (Den) 21-13 23-21 (33m)
Gold: Mohammad Ahsan & Hendra Setiawan (Ina); Silver: Matthias Boe & Carsten Mogensen (Den); Bronze: Cai Yun & Fu Haifeng (Chn), Ki Jung Kim & Sa Rang Kim (Kor)
(1) Wang Xiaoli & Yu Yang (Chn) bt (8) Hye Wong Eom & Ye Na Jang (Kor) 21-14 18-21 21-8 (69m)
Gold: Wang Xiaoli & Yu Yang (Chn); Silver: Hye Wong Eom & Ye Na Jang (Kor));
Bronze: Christinna Pedersen & Kamilla Rytter Juhl (Den), Tian Qing & Zhao Yunlei (Chn)
(3) Tontowi Ahmad & Liliyana Natsir (Ina) bt (1) Xu Chen & Ma Jin (Chn) 21-13
16-21 22-20 (74m)
Gold: Tontowi Ahmad & Liliyana Natsir (Ina); Silver: Xu Chen & Ma Jin (Chn); Bronze: Baek Choel Shin & Hye Won Eom (Kor), Zhang Nan & Zhao Yunlei (Chn)
Gold Silver Bronze
China 2 2 4
Indonesia 2 - -
Thailand 1 - -
Korea - 1 3
Denmark - 1 1
Malaysia - 1 -