Maybe Fed is trying to inspire Delpo to be the one to succeed him on the throne as he likes Delpo more than he likes Djok and Rafa )
Also, Delpo has deferred to Fed in many if not most of the matches they've played. It almost seems Delpo is afraid to beat Fed, though he has done it here and there, in stunning fashion too.
"He looked like he was trying to imitate Sampras when I first played him." Agassi in Facing Federer