Basically it comes down the WTF whether or not Djokovic's record is even in discussion this year. If he doesn't win that means that he will likely add 1 to 2 losses to his 6 loses this year. That will make 6 losses. Now if that is the case, his win/loss record is far behind Federer 2006. At the moment his Grand Slam record is behind Federer's 2006 (Federer got to all 4 GS finals, Djokovic didn't). He will have won about 15 less matches as well. And Federer's 4 Masters + WFT > 5 Masters for Djokovic. So hard to think of what criteria people would even discuss this season as being the best ever.
(The only thing would be perhaps would be being consistent winner over the number 2 player)