At this stage in Rafa's career, it has to be about the majors.
Roland Garros and his 14th major is the prize, not these relatively insignificant slower hard court masters in the USA. The late winter and early spring slower hard courts, including the AO, have caused most of his injuries and problems later on. And yet, and yet, he stubbornly keeps playing these even with his two masters exemptions.
My recommendation: Rafa, forget Miami, go back to Manacor and get on the clay and practice 4-6 hours a day on returns and backhands when the back feels better. Maybe even arrive in Monte-Carlo a week early, get some practice in, and enjoy the view. I'm sure he could find some adequate players with whom he could practice. Many players use Monte-Carlo as their base.





Respectfully,
masterclass