This is my opinion anyways...
When playing A game on CLAY, Nadal is unstoppable ....Djoke or NoDjoke. It becomes interesting when Nadal level dips. Thats when he is passive and he tries to Loop the ball back in play and waits for opponents error. Even at this level, his game is good enough against almost everyone but not Djokovic. Djoker has the neccessary weapons to track down Nadal's loopers and hit them with interest.
I wouldnt put too much stock on Nadal's recent losses. This guy hasnt played a match for months due to injury. Though he won a few tournaments (incl Indian wells), it takes time to round up into form -especially for Nadal's game. Come FO, i think he will be fine.
Lets look at Barcelona. Nadal's game is no where near what it used to be. Sloppy starts (0-3 holes), questionable shot selection, Poor BP conversion, etc all symptoms of a player trying to come back into form.
I am unbeaten against Federer, Nadal , Sampras, Agassi.