The funny thing about Murray and Del Potro match-up is this.
Tennis loses in the worst way ever.
Murray doesn't defeat him so much via technique. He defeats more relying on fitness. How pathetic is that? So Del Potro has the talent and tools to defeat Murray anywhere at anytime, but the problem is, his fitness lets him down, and thanks to that, Murray can defeat him at slams in that manner.
I'd take del Potro over Murray any day. I think Nadal might actually be right if del Potro plays consistently and isn't hampered by his wrist injury.
Maybe Nadal would fall out of the top 4.
"But certain interests of particular people are so important that it would be wrong - morally wrong - for the community to sacrifice those interests just to secure an overall benefit. Political rights mark off and protect these particularly important interests. A political right, we may say, is a trump over the kind of trade-off argument that normally justifies political action." - Ronald Dworkin (RIP)