Rafael Nadal reignited the debate over who will finish with the most Grand Slam titles in men’s tennis after he won his 19th major at the US Open. The 33-year-old Spaniard withstood a thrilling fightback from Daniil Medvedev to win his fourth title at Flushing Meadows, after arguably the greatest US Open showpiece.Nadal is now within one of Roger Federer’s haul of 20 Grand Slam titles and three ahead of world No 1 Novak Djokovic.The ‘Big Three’ have won 33 of the 40 Grand Slam titles over the past decade and have shared the last 12 majors between them to underline their dominance. List of most Grand Slam men’s singles titles Roger Federer 20 Rafael Nadal 19 Novak Djokovic 16 Nadal will be confident of defending his French Open title once again next year and winning a 13th Roland Garros crown, while Djokovic will begin the season as the Australian Open defending champion. Also See: Nadal edges Medvedev in US Open epic How Nadal won US Open thriller Both Nadal and Djokovic have won two Grand Slams this year after the Serb saved two championship points to beat Federer in the longest Wimbledon singles final.Who do you think will end…