Rafael Nadal, Shanghai Masters
Tennis - Shanghai Masters tennis tournament - Shanghai, China - October 12, 2017 - Rafael Nadal of Spain celebrates his win against Fabio Fognini of Italy. Reuters / Aly Song

Rafael Nadal, the 16-time Grand Slam champion, clinched the year-ending World No. 1 ranking on Wednesday after defeating South Korean Hyeon Chung in the first-round of the Rolex Paris Masters. Nadal will finish a season at the apex of the tennis world for the fourth time in his career -- after 2008, 2010 and 2013.

It has been a remarkable comeback story for Nadal. In 2016, he suffered a first round defeat to Fernando Verdasco at the Australian Open before suffering upset losses at the French Open and US Open, besides skipping the Wimbledon due to a wrist injury. The year also saw Nadal not reaching a Grand Slam quarter-final for the first time since 2004, fuelling speculation of a potential retirement from tennis.

"One year ago, for sure I never dreamed about being number one again at the end of the season. It has been an amazing year. It was impossible for me to think about coming back from a tough period without playing, and with so many injuries in the last couple of years," an emotional Nadal said in his on-court interview after Wednesday's 7-5, 6-3 victory over Chung.

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The 31-year-old has been quick to prove naysayers wrong, winning two out of the four Grand Slams in 2017 besides pushing arch nemesis Roger Federer to a five-set classic at the Australian Open final. The Spaniard has captured a total of six titles in 2017 -- the French Open, the U.S. Open and two ATP World Tour Masters 1000 trophies.

At 31, Nadal will become the oldest player in ATP Rankings History to finish a year at World No. 1 when he's presented with the trophy at the Nitto ATP Finals. It will be held in London from Nov. 12-19.

"I’m very, very happy for everything. It has been an amazing year. One year ago, for sure I never dreamed about being World No. 1 again at the end of the season. It’s something that means a lot to me. But the season is not over. It's about the passion for what you are doing. It's about the mentality of waking up every morning with the right motivation to go on court and improve something. The passion to improve something and practice every day with the right attitude to try to make that happen," Nadal added.

Rafael Nadal was a lock to finish the year World No. 1 after Roger Federer made a surprising decision to withdraw from the ongoing Paris Masters. Federer, after winning his eighth Swiss Indoors title, needed to put up strong performances at Parris and the Nitto ATP Finals (Nov. 12-19) to challenge Nadal's throne. However, the Swiss Master cited a back injury and decided to forego his quest to finish World No. 1 for the first time since 2009.