#2 Rafael Nadal (58-7)
Rafael Nadal started the season with a run to a fifth Australian Open final. But the Spaniard endured his first-ever straight sets final loss, going down to Novak Djokovic in a lopsided title match.
Following an early exit in Acapulco (lost to Nick Kyrgios), Nadal withdrew from his semifinal with Roger Federer at Indian Wells. The Spaniard then endured a trio of semifinal exits in Monte Carlo (Fabio Fognini), Barcelona (Dominic Thiem) and Madrid (Stefanos Tsitsipas) on his favourite turf, before beating Djokovic in a three-set final to win his 9th Rome title.
A rejuvenated Nadal overcame Dominic Thiem in a repeat of the pair's 2018 title match, to win a record-extending 12th Roland Garros title. He then made the semis of Wimbledon where he lost to Roger Federer in four sets.
Nadal recorded his first-ever successful title defence on hardcourt when he beat first-time Masters 1000 finalist Daniil Medvedev to win a record-equaling 5th title at the Coupe Rogers in Montreal and a record-extending 35th Masters 1000 title.
Four weeks later, the pair met in the title match of the US Open, where Nadal squandered a lead of two sets a break and almost squandered a double break lead in the fifth before winning his 4th US Open and 19th Grand Slam title. Nadal's triumph marked the first time in eight years that the Spaniard and Djokovic had swept all four Grand Slam titles in a year.
Nadal recorded his 50th match win of the season at the Paris Masters before withdrawing from his semifinal against Denis Shapovalov. At the ATP Finals, Nadal saved a match point at 1-5 on his serve in the third set of his round-robin match win against Medvedev to remain in contention for a semifinal spot.
Nadal ultimately couldn't reach the semis, but Djokovic's defeat against Federer confirmed the Spaniard as the oldest year-end No. 1. Nadal's fifth year-end No.1 finish also took him level with Jimmy Connors, Roger Federer and Novak Djokovic in the all-time list.
The Spaniard was not done for the season though. At the revamped Davis Cup Finals in Madrid, Nadal registered five singles wins and three doubles wins in eight matches across five days to seal a sixth Davis Cup title for Spain.
In the process, Nadal recorded his 29th singles match win at the Davis Cup and extended his winning streak in the competition to 29, with his only loss coming on his tournament debut against Czech Jiri Novak in 2004.
Also read: Rafael Nadal's 5 memorable match wins at the US Open.
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