If we agree that Federer would beat Agassi (and it's true Agassi played him close from time to time), and Djokovic can beat Federer by essentially being a human backboard, I don't see that Agassi would have a chance against Djokovic.
Sampras used to say one problem with Agassi was his footspeed. He just didn't run that fast. Agassi used to try to rip a forehand to Sampras's forehand. Sampras would then hit a reverse forehand and it would come back with angle and pace. Djokovic can do that more easily than Sampras.