There was a lengthy rain delay during Garbine Muguruza's match with Sloane Stephens, but the Spaniard adapted and overcame.
Lorenzo Musetti was three when Stan Wawrinka made his Internazionali d'Italia debut but the home hope downed the three-time grand slam king.
Jack Nicklaus' major haul of 18 remains tantalisingly out of reach for Tiger Woods, who is ruing the the relentless march of time.
Dominic Thiem was a worthy winner of the US Open, according to Rafael Nadal.
Former world number one Andy Murray made his grand slam return at the US Open and will get another shot at Roland Garros.
There were straight sets victories for Kei Nishikori and Gregor Dimitrov in Rome on Monday, but Dan Evans and Felix Auger-Aliassime are out.
Jet lag could not hold back Elena Rybakina as she gained revenge over Ekaterina Alexandrova in Rome on Monday.
Rafael Nadal preached the importance of self-control after being asked about Novak Djokovic's stunning US Open default.
Novak Djokovic, disqualified from the US Open this month, can make no promises about possible rule-breaking in future.
After falling short to Dominic Thiem in the US Open final, Alexander Zverev rued missed opportunities.