Here's my wild guess, in order of least to most likely to be "touched."
I think you did a good job of ordering them. I'll add a few comments
- 14 titles at one Grand Slam - I just can't see anyone ever matching this. I mean, anything is possible, but to me this is Rafa's most untouchable record - or at least his most distinctive.
Definitely the most distinctive, because it's a Major. As a lot of players pointed out when honoring the achievement, first of all you have to qualify for one Major at least 14 times, which, by itself is a thing. As we go down this list, we have to note that it takes a long career to get to some of these numbers, which is already a hump to get over, and then play consistently great for that long. It is possible that Novak could get to 14 at the AO, though that's looking unlikely. But even still, it's not at RG, so that record will stand for a long time. (I guess 14 years in the minimum, at this point, given that Alcaraz is young, and has a streak of one.) Like you, though, believe this record won't be beaten.
2. Win % in best-of-5 on clay (97.1%) - this is arguably more untouchable than the above.
137-4 in Bo5 on clay has to be untouchable, for two reasons. The first is obvious, (in that it's mind-boggling,) and the second is that Nadal played in an era when DC and MS1000 finals were also played in Bo5, so there was more opportunity. But as to the win pct., even if you put the minimum number of matches at, say, 50, (which is the equivalent of 7 French Opens+,) it would be hard to see someone beating 97.1% over a career. Djokovic, by comparison, who has won the French Open 3 times, has an 85.19% (92-16) win rate in Bo5 there. I don't know how many other clay Bo5 he played and won, but it can't be many, and there are likely to have been losses.
3. Most titles on clay (63) - a half step behind the first two, only because a "21st century Vilas" (or Muster) could theoretically come along and dominate lower clay titles. Still very, very unlikely.
If someone else gets 63+ titles on clay, of the quality of the ones that Rafa won, more power to them. Because if they're filled out with 250's, etc., like Vila's were, it won't be looked upon as the same. But I take your point.
4. Most wins against the #1 (23) - This one is a step down, but still probably untouchable - because it combines not only requisite greatness but also a certain combination of other factors: namely, several truly great players playing at the same time - but not too many (or too few). If you had one guy who dominated, he would be #1 all the time and therefore never have a chance to beat the #1 (e.g. Roger in 2004-08); if you had too many #1s swapping around, then one of them wouldn't be great enough to be beating everyone else a lot without being number one. I suppose Alcaraz and Sinner could swap the role for the next 8+ years and one have have the match-up edge and get there, but it would be difficult.
To be fair about this stat, Rafa spent 3 solid years as #2 to Roger's #1, when he was beating Fed a lot. That popped out to me, right away. And then there was a lot of trading #1/2/3 between the Big 3. As you say, it takes truly great players playing at the same time, so when you Rafa was #2 or #3, and beat #1, that was also about the timing of the win and their rankings. But, again, that's why it could be hard to match. It would be sort of pathetic if you had a player who beats #1s regularly, but doesn't get to #1 often enough to off-set the number.
5. Youngest to win Golden Slam - this one is probably untouchable just because it requires timing, in addition to ability. Meaning, the Olympics has to come at just the right time in combination with enough Slams won. Alcaraz missed the cut, unfortunately, because he'll be 25 at the next Olympics.
With the Olympics, it's a lot about timing, and Rafa was hitting a peak in 2008, which also happened to be an Olympic year. Still, he completed the career-Slam in 2010, at 24, so that's still younger than Laver, in the Open Era. However, as has been pointed out, Alcaraz can do that one younger, either this coming AO, or at either of the next 2 after that.
6. 10 titles at four tournaments - this will be hard to touch, but is a bit more possible.
7. Most consecutive wins on a single surface (81 matches on clay) - a great record, but touchable, though very very difficult.
8. Most consecutive years winning a Grand Slam (10) - this seems inevitable, though Rafa did it largely through owning Roland Garros, but a player like Alcaraz could do it through being so balanced on surfaces, but also because he seems to go through multiple hot periods in a year. 3 down, 7 to go!
9. Clay Slam - also great, but also touchable. Muster came close in 95 (1 GS, 2 Mas) but didn't play in Hamburg. But probably the most touchable of the nine.
I'd say 1-3 are truly untouchable, 4-6 may or may not be every touched but could easily hold for decades to come. 7-9 will be hard to touch, but more possible.
Already Touched
- Most titles as a teenager - this is a record if they mean in a single year (11 in 2005), but not "as a teenager" like it is written, as Borg has one more (17 to 16).
- Grand Slam title on every surface (clay, hard, grass) in one year - Novak did this in 2021. The article got it wrong about Laver in 1969, because the USO was on grass.
- Completing the Grand Slam twice - Laver and Novak both did this.
I'll leave the rest, because I have nothing to add to your assessment. As I said, I agree with how you rank them.
