What if there were 3 grasscourt Masters instead of 3 claycourt Masters?
I conducted a quick analysis to estimate how many Masters titles the big 4 would have if there were three Masters 1000s events on grass each year instead of 3 on clay. The methodology was as follows: remove each player's clay titles from their totals (remove 6 for Federer, 2 for Murray, 25 for Rafa and 10 for Novak). Then, find out the number of claycourt Masters events played by each player over the course of their career: (Rafa: 46, Roger: 45, Novak: 38, Andy: 32) and convert these to grasscourt Masters tournaments played. Lastly, multiply the number of tournaments played by their Expected Success Rate at each grassocurt Masters, which is based on their actual success rate at Wimbledon (Federer: 8/21, Nadal: 2/14, Djokovic: 5/15, Murray: 2/12). This gives us the predicted number of masters events each player would have on grass based on their real performance at Wimbledon, and these are added to their total Masters count.
The results:
1. Federer: 39 titles
2. Djokovic: 38 titles
3. Murray: 17 titles
4. Nadal: 17 titles
Federer would have benefited significantly, and is significantly held back by the prevalence of claycourt masters. Djokovic and Murray would have benefited marginally, and Nadal would have suffered greatly in his Masters tally.
Before anyone gets upset, this is just an overly simplistic hypothetical estimate. I know that if there were this many grass tournaments and no clay masters, Rafa might have changed his playing style and had more success. I also know that Wimbledon performance would not be perfectly correlated with grasscourt Masters performance, or that this change may have reduced some players injury periods and extended others. I'm just a guy who enjoys tennis and enjoy statistics and likes to combine the two for fun.