That was a frustrating turn of events, for sure, for those of us who like Musetti, and don't care so much for Djokovic. And when it's harder to see the injury, people get upset. Last year, when Novak pulled out abruptly v. Zverev after one set, he got booed. So, one could argue that, karmically, he had one owing, but two seems a bit much, with the Mensik withdrawal. That IS the kind of luck that an older player needs. Though, Sinner breezed through, so I'm not sure it will help him in the SFs, anyway.
Musetti had every reason to want to stay in that match. Now that your hot Sicilian blood is calmer, I hope you know that.