Well, the way I see it, lacatch, is that the only other obvious candidate for Roland Garros is Novak, and who knows where he'll be at in a few months. He is really struggling, far from his #1, Slam-winning form.
Andy is also a candidate, as he has improved year by year on clay. But I still place him behind Rafa and Novak on the depth chart.
After Andy it is a big drop off to a group of players that includes Dominic Thiem, perhaps the future dominant clay courter; Stan Wawrinka, who is always dangerous but also erratic; Roger Federer, who is unlikely to win another RG, but could be there if the draw opens up and upsets occur; and perhaps a surging Dimitrov, a solid Nishikori, a wildcard Kyrgios, or even a maturing Zverev.
But the bottom line is that even if Rafa isn't the usual distant favorite, he's right there on the short list for most likely candidates and, I think, is currently the first of the bunch. I think Novak will eventually rebound, but not to 2015 form - maybe, if he's lucky, more like 2012-14 form, which would probably put him coeval with Rafa on clay.
In summary, my RG likely winners list is, in order:
1. Nadal
2. Djokovic
3. Wawrinka
4. Murray
5. Thiem
6. Federer
7. Dimitrov
8. Nishikori
And then everyone else - Kyrgios, Cilic, del Potro, Zverev, etc.
