I say he has a legitimate shot of winning all 4 tournaments. Let's see what he's defending: first off he loses the 90 points in Monte Carlo for not playing at all, Estoril he didn't play last year so unless he loses in the first round he will pick up points here, 360 SF points in Rome, and all 2000 points with the FO title, that's 2450 points with little chance of losing a lot.
As for Rafa: he's defending 3280 points this clay season (1000 Monte Carlo title, 500 Barcelona title, 1000 Rome title, 600 Madrid F, and 180 French Open 4th round). There's little chance for Rafa to get back to #2, he has to defend 3 titles and a runner up, can go up at the FO, but to become #2 again will be tough as early as the end of the FO, he'll still be only #3 at best.
what about the 1000 pts he needs to defend for Madrid?