Since Rafael Nadal won the US Open, his second Grand Slam of 2019 and 19th overall, much has been written about him moving to within one of Roger Federer's record tally of 20 Grand Slams. The race to be the greatest male tennis player of all time, which also includes Novak Djokovic, is well and truly on.
Having missed a golden opportunity to beat Djokovic at Wimbledon, Federer has been marooned on 20 titles since January 2018 as his rivals have continued to close in on him.
The general consensus is that the player that retires with the largest haul of Majors will go down in history as the best ever. However, I believe there is a case to be made that Nadal is already greater than his long-time Swiss rival.
There are a number of factors to be considered in this debate, which are elaborated as follows:
Grand Slam titles won
There were times in the past when it looked unlikely that anyone would ever catch Federer; such was his hold over the sport's top titles.
However, Nadal's relentless dominance of the French Open guarantees him at least one Grand Slam a year, while he has continued to give himself opportunities to win on hard courts. Wimbledon is the only Major championship where he fails to really excel; he hasn't reached a final on the grass courts of SW19 since losing to Djokovic in 2011.
Nadal has 19 titles overall - 12 at the French Open, four at the US Open, two Wimbledon crowns and one Australian Open. He has also been runner-up in a further eight events.
Federer is one ahead. He has five wins each in Australia and the US, eight Wimbledon victories and a solitary French Open crown. He has been runner-up on a further 11 occasions.
They have both shown the ability to win on every surface. However, Federer was never able to beat Nadal on the clay of Roland Garros, while Nadal did defeat Federer on his favoured grass courts of Wimbledon.
In this category you have to give Federer the edge until Nadal matches his total, which will most likely happen at Roland Garros in 2020.
Through the course of their storied careers, Nadal and Federer have met 40 times - with Nadal leading 24-16 overall.
Go back to 2014 and this was even more heavily skewed in Nadal's favour, as he led 23-10 at that stage. Federer pulled back considerably with a five-match winning streak on hard courts between 2015 and 2017.
However during that period the pair never met on Nadal's favoured claycourt surface. They have one victory apiece in 2019.
The numbers don't tell the full story, but for a long period it was obvious to all followers of the sport that Nadal had Federer's number, particularly on the biggest occasions when his incredible mental strength and dogged determination were often enough to wear down the prodigious talent of Federer.
Perhaps what illustrates this point best is a look at their record when they have played each other in Grand Slam finals. They have met each other on 10 occasions with the sport's biggest prizes at stake.
Nadal has won seven of those matches, winning four times at Roland Garros, twice at Wimbledon and once at the Australian Open. Federer has beaten Nadal twice at Wimbledon - in 2006 and 2007 - and once in Australia in 2017.
On the biggest occasions Nadal has always had the upper hand over his rival.
This is one category where Federer is streets ahead of Nadal. His excellent injury record and incredible consistency across all surfaces have seen him top the rankings for a record total of 310 weeks.
Nadal, who has often been forced to play a reduced schedule due to his troubling knees, has been ranked the best player in the world for a total of 190 weeks. At the age of 33 it is unlikely that his sometimes fragile body will allow him to play long enough to match Federer's record.
Federer also holds the record for most consecutive weeks at the top. with an incredible 237-week spell as the world's leading player. The longest Nadal has managed is 56 weeks.
The Swiss has also finished as year-end number one on five occasions to Nadal's four.
Titles and match-winning percentage
Arguably Federer's best achievement of this calendar year was winning his 100th tournament. He now has 102 to his name, which is second only to Jimmy Connors.
While winning those trophies Federer has won 1,227 matches at a win percentage of 82.1%. He has been on the losing side of the net on just 267 occasions. Apart from his Grand Slam crowns he has won a record six World Tour Finals trophies and 28 ATP Masters 1000 events.
Nadal, who it must be remembered is five years Federer's junior, has won 84 titles and is fourth on the all-time list. He has won 966 matches at a win percentage marginally better than Federer's - 83.1%.
Unlike his great rival Nadal has never managed to win a Tour Finals title, often arriving at the season-ending event out of form or carrying an injury. He has reached the final on two occasions, losing in 2010 and 2013.
Nadal has seven more ATP Masters 1000 event wins than Federer, with his dominance on clay courts contributing significantly to this record tally.
It is incredibly difficult to split them here. Federer is currently way out in front but Nadal, unless struck down by a career-ending injury, has a lot more years left in the game. Their win percentages are astonishing and remarkably similar.
Representing their country
Along with their individual brilliance, both players have been lucky to play in an era where they have been supported by their countrymen in some of the biggest team events in the world.
Nadal has played during a period when there has been incredible depth within Spanish tennis. On the other hand, Federer's fellow countryman Stan Wawrinka has also enjoyed an excellent career that has seen him win three Grand Slams.
As is becoming a recurring theme throughout this article, it is very difficult to split them.
If we start by looking at the Davis Cup, Nadal clearly has the edge in terms of number of competitions won. He has been part of the winning Spanish team on four occasions - in 2004, 2008, 2009 and 2011 - with his record leading to suggestions that he is the greatest Davis Cup player of all time.
In singles matches Nadal has won 22 matches and lost only once, while winning five and losing four doubles matches. He has also won two Olympic gold medals - one in singles in 2008 and one in doubles in 2016.
In contrast Federer has only won the Davis Cup once, in 2014, which was yet another box ticked off in his record-breaking career. However his individual performances have been brilliant, as he has won 40 singles matches and lost just eight. He also has an Olympic gold medal in doubles (alongside Wawrinka in 2008) and a silver medal in singles at the 2012 edition.
Although they have both been successful in this department, Nadal takes the edge courtesy of his multiple victories in Davis Cup and his singles gold medal at the Olympics.
Writing this article has made me realize just how incredible both players have been throughout their careers. Like Cristiano Ronaldo and Lionel Messi in football, the rivalry between Federer and Nadal has driven them to heights previously unseen in the sport.
Their contrasting styles - Federer oozing talent and elegance, Nadal the ultimate street-fighter who never knows when he is beaten - have made for some of the greatest matches in tennis history.
The question I've attempted to answer in this article is this: if they both retired today, who would be considered the best ever?
While I'm sure many would still lean towards Federer, in my opinion Nadal edges it based on their record against each other. The Spaniard started as a claycourt specialist without making too much impact on hard or grasscourts. However, he found a way to win and made himself into one of the greatest all-court players of all time, regularly defeating Federer on the biggest occasions.
To beat Federer, the greatest grasscourt player of all time at his peak at Wimbledon in 2008 was a truly remarkable achievement. Federer, on the other hand, was never able to work out a way to beat Nadal on clay, and for me that is why Nadal should be considered the greater of the two.
It's incredibly close, but for me the balance just tips slightly in favour of Nadal.