The Italian was two sets up when he retired, leading 6-4 6-3 1-3.
“Today I played one of the best matches of my life, both in terms of importance and the weight of the ball, making things difficult for the most successful player in the history of tennis,” said the world number five, adding that he thinks he may have torn a muscle.
“This is what makes me most angry—I don’t understand the reason for these injuries,” added Musetti.
“I felt it at the beginning of the second set … there was something strange in my right leg.
“I continued to play, because I was playing really, really, really well, but I was feeling that the pain was increasing, and the problem was not going away.
“At the end, when I took the medical timeout … when I started to play again, I felt [it] even more and the level of the pain was getting higher and higher.
“Honestly, I never imagined the feeling of leading two sets to zero against Novak and playing like that.
“Having the lead in the match like that and being forced to retire is something that, of course, I could never imagine.
“Of course, it’s really painful.”
ANSA