He needs match play and the intensity of a match to get into his rhythm, get into the zone, and feel the ball.
Novak had 2 easy games, one was retired without a game, the other was retired just played 6 games. He is now very energetic to play against remaining players, he will be the winner easily.
It is good for him if the other players retire because then he does not have to play that hard in the end games. So he rests himself for the next match that really matters. So this is his advantage then if they all just fall before finishing a match.
Yup, now Novak is ready for game, and i am sure that he will win this one with Murray in finals, that will be good game as usual whent this two players clash