What's Djokovic achieved to make him a grand slam contender? Nothing.
Coming from me, a non-fan of Djokovic, I would say he has shown that he is a contender. If he didn't run into Fed, there is high chance he would have played his first slam SF this year. He has won 3 good tournaments. In matches he has lost to top players, in many occasions he has not been wiped off court.
The only thing my opinion is NOT based on are his claims of "being in control" two sets down to rafa in rg last year.... Certainly the guy gets full points for self belief.