I'm afraid that the frequent injections meant to heal the tendon have actually made the tendon weaker and susceptible to tears. I think Nadal needs better medical care than he has received so far. It is a bad sign that the tendon is torn yet it took the doctors many weeks to come to that realization. When the stakes are this high relying on quacks is stupid.
Some how with his money, i highly doubt it's down to bad medical advice.