I used to hate fishing, but I'll make an exception.
Nadal will do as he pleases, and if he pleases he'll play and acquit himself well. What has it been? A six-eight month layoff? For most players that's touch and go when they return, but Nadal will make an impression if he plays. QF, at worst.
Well he had a 1 month layoff in 2009 and still struggled to make the USO SF and we know his results from that point on until the 2010 clay season...and this included a QF loss in Australia. I think QF is the furthest he will go but still impossible to say.