err, what ?
Rosewall is ahead, but not by much in terms of achievements.
4 amateur slams, 15 pro majors, 3 open era slams+1 depleted open era slam+2 WCTs
An amateur slam doesn't come close to a full open era slam.
Let say for a fun excercise, we put 1 amateur slam and the depleted open era slam as 0.5*major
Let say we have each pro majors and the WCTs as 0.75*major
totally we get : 5*0.5+17*0.75+3*1 = 2.5+12.75+3 = 18.25 majors
Nadal has 16 majors as now.
Nadal has been #1 for 4 years.
Rosewall is #1 for either one of 60 or 61 (choose one among them, you can't have both, you can't have the cake and eat it too), #1 for 62 and 63 clearly.
64 is close. Arguable #1.
70 and 71 are weaker claims tbh.
I don't see more than 4 years as #1 for Rosewall tbh.
He was #2 guy for quite some time (just like Nadal)
I have 15 majors for Rosewall in a hypothetical open environment. (IMO , margin of error was 2-3, so IMO he ends up with 17-18 majors tops. I don't think he does, but anyways.)
https://tt.tennis-warehouse.com/ind...-etc-in-hypothetical-open-environment.595606/
Nadal has won 30 masters titles and some other smaller titles as well. So he has that part covered as well along with Rosewall (given the context of their respective times).
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and now coming to the more important point. why does rating have to be based on achievements only ? There are other factors like peak play, consistency, longevity, dominance etc. etc