I've also have written on this topic and have tweeted frequently about it, so I was grateful to see someone else use their platform to bring attention to this topic. The reason I am writing this response, however, is Matt's assertion that a Calendar Grand Slam is a greater achievement than a non-calendar Grand Slam.
Matt isn't alone in this view. In fact, he is part of the majority. I have always argued that the difference is completely arbitrary. Four in a row is four in a row regardless of order is what I have been saying since before Djokovic won Roland Garros.
Matt certainly isn't the first to disagree with me on that point, and I've long considered addressing what I have always considered to be a misconception. However, Matt threw a wrinkle into this. His reasoning is far more complete than fans who think calendars matter. I hope I accurately represent his views here.
For Matt, not only is a non-calendar slam not as impressive as a calendar slam, but there is a hierarchy even among the different kinds of non-calendar slams. If the order includes winning Roland Garros and Wimbledon, it is greater than winning Wimbledon first and saving Roland Garros for last. Similarly, winning Roland Garros, Wimbledon and the US Open in order is more impressive than winning the US Open first and coming back for the other three afterwards.
The reason is that less time separates the majors. If someone wins Wimbledon first, they don't have more than a full month between each major en route to four in a row. The assumption being that more time between majors makes winning them consecutively easier. It's a widely accepted idea, but nobody has ever put it to the test mathematically. I want to do that in just a bit.
There are four different ways to win four in a row. You can win four in a row starting at the Australian Open, Roland Garros, Wimbledon, or the US Open. I have argued that it doesn't matter, many have said starting at the Australian Open is best and the rest are secondary because they are non-calendar, and Matt says that all four are unique. So who is right?
As I write this sentence, I don't yet have the answer to that question. Before I even begin researching, I want to tell you how I am going to determine who is right. That way everyone knows my methodology is objective. This way everyone knows that I didn't research first and then cherry pick what supports my arguement.
My methodology
Every run of four consecutive majors is comprised of three doubles and two triples. A double is winning two slams in a row and a triple is winning three in a row. If a player wins a Calendar Slam, they completed the AO-RG double, RG-W double, and W-USO double, but they did not achieve the AO-USO double. When Djokovic won four in a row, he won the W-USO double, USO-AO double, and AO-RG double. For triples, Djokovic won the W-USO-AO triple and the USO-AO-RG triple, but not the AO-RG-W triple or the RG-W-USO triple.
My plan is to rank the doubles from most difficult to least difficult and then do the same for the triples. Using that ranking, I will determine in which order it is hardest to win four in a row.
I am going to look at three stats from all men's tennis majors since 1988. I pick 1988 because that was when the Australian Open switched to hard courts and by then had already been scheduled for January. Data from before 1988 really isn't relevant in determining how difficult it is to win consecutive majors today.
These are the three stats
1. Number of times the double or triple has been achieved
2. Number of times a player has reached the final of all the majors in the double or triple
3. How well the winner fared at the following major (for triples I will look at the results only if the player won the previous two majors)
*Data does not include any of Djokovic's four most recent majors
Results
Doubles
AO-RG: This double was won twice (hadn't been done since 1992). Australian Open winners went on to go 119-18 with three withdrawals at Roland Garros. Finalists at the Australian Open reached the final at Roland Garros 11 times.
RG-W: This double was won three times (three consecutive years, 2008-10). Roland Garros winners went on to go 76-20 with five withdrawals at Wimbledon. Finalists at Roland Garros reached the Wimbledon final 13 times.
W-USO: This double was won nine times. Wimbledon winners went on to go 129-18 with one withdrawal at the US Open. Finalists at Wimbledon reached the finals at the US Open 17 times.
USO-AO: This double was won seven times. US Open winners went 119-18 with three withdrawals at the Australian Open. Finalists at the US Open reached the final at the Australian Open 23 times.
Triples
AO-RG-W: This triple has been done 0 times since Rod Laver did it in 1969. The two players that won the first two legs combined to go 6-2 at Wimbledon. Players who reached the final of the first two legs reached the Wimbledon final 6 times.
RG-W-USO: This triple has been completed 1 time (Nadal 2010). The three players who won the first two legs combined to go 18-2 at the US Open. Players who reached the final of the first two legs reached the US Open final 7 times.
W-USO-AO: This triple has been completed 4 times. The nine players who completed the first two legs of this triple combined to go 48-5 at the Australian Open. Players who reached the final of the first two legs reached the AO final 9 times.
USO-AO-RG: This triple has been completed 0 times since Don Budge did it in 1938. The seven players that completed the first two parts combined to go 29-7 at Roland Garros. Players that reached the final of the first two legs reached the Roland Garros final 7 times.
Ranking the Difficulty
Doubles (hardest to easiest)
1. Australian Open-Roland Garros
2. Roland Garros-Wimbledon
3. US Open-Australian Open
4. Wimbledon-US Open
Triples (hardest to easiest)
1. Australian Open-Roland Garros-Wimbledon
2. US Open-Australian Open-Roland Garros
3. Roland Garrros-Wimbledon-US Open
4. Wimbledon-US Open-Australian Open
This is certainly up for debate. The top two spots on both lists are virtual ties. It just depends on what stat you think is the better indicator. One interesting note is that nobody who has won Roland Garros has lost at Wimbledon in the semifinals. A lot failed to reach the semifinals, but of the seven that reached the semifinals, they went 7-0 in the semifinals and 3-4 in the final.
It seems that winning Roland Garros does take a massive physical toll on the body, but if the player that won Roland Garros can survive the first few rounds at Wimbledon, they have a great chance to bring home the trophy.
Meanwhile, maintaining a high level of play from the Australian Open to Roland Garros appears to be one of the biggest tests in tennis. There are five Masters Series 1000's between the two majors, so the confidence of having won the Australian Open doesn't naturally flow over to the next major. That kind of confidence has to be maintained over a number of brutal tests. At Roland Garros, 17 of 28 Australian Open winners reached the second week, but failed to win the trophy. Of the remaining 11, two withdrew, seven lost in the first week, and only two won the trophy and both of those were over two decades ago within four years of each other.
Conclusion
Ranking of the four ways to win the Grand Slam (hardest to easiest)
1. Starting from the US Open
2. Starting from the Australian Open (Calendar Slam)
3. Starting at Wimbledon
4. Starting at Roland Garros
Starting from the US Open includes the three hardest doubles and the two hardest triples, so that is by far the hardest way to win a grand slam. Starting from Roland Garros includes the three easiest doubles and the two easiest triples, so that is clearly the easiest.
The two that are left are the Calendar Slam and the Nole Slam. The Nole Slam doesn't include the second hardest double or the hardest and third hardest triples. The Calendar Slam doesn't include the third hardest double or the second and fourth hardest triples. Therefore Calendar Slam is slightly harder than the Nole Slam.
My Thoughts
There definitely does seem to be a hierarchy as Matt claimed. However, less time between majors certainly is not the determining factor in which is hardest. Each of the four ways to complete the Grand Slam present unique challenges. None of the four is like another.
Also, elevating the Calendar Slam above the non-calendar slam is certainly an arbitrary difference as the data shows here. There is nothing more impressive about doing it before the calendar changes. The way Djokovic completed the Grand Slam was the third hardest way to do it, so that destroys the excuse that media used when they said only the Calendar Slam matters.
Final Thought
I want to echo Matt's main point, because at the end of the day, I agree with him. Tennis journalists missed a massive opportunity to help this sport reach the generic sports fans, who don't typically follow tennis. Instead of focusing on Djokovic's pursuit of history, they trotted out the old narratives of "the elusive Roland Garros trophy." They copied and pasted stories from the year before instead of realizing a new kind of history was about to be made.
One interesting thing came out of my research that even I, as a massive Djokovic fan, didn't know. Djokovic was the first player since Don Budge in 1938 to win the US Open, the Australian Open and Wimbledon in order. Why didn't I know that? Why didn't I care? Because Djokovic had won four in a row. I wasn't going to be excited about three in a certain order when four in a row just happened. The achievement of those three in a row, was secondary, so it got completely buried that even I didn't know.
That is how the media should have treated the Career Slam. Djokovic had just won all four in a 12-month span. How could any journalist think it is even noteworthy that he had won all four at some point or another in his career? That achievement would be overwhelmingly obvious given the fact that he had done it in a 12-month span. Ultimately, the media dropped the ball on this one and tennis as a sport (not just Djokovic fans) missed an opportunity.