The top-ranked Serb was mostly courteous with the chair umpire during a 6-3 6-2 win over local wildcard Salvatore Caruso on Wednesday.

When the umpire came down to inspect a ball mark on the red clay early in the first set and made an overrule in Caruso's favour, Djokovic just replied, "Yup," and rubbed out the mark with his red sneaker.

When Caruso impressed him - the Italian hit 13 winners to Djokovic's 12 - the Serb said, "Bravo."

Djokovic's only testy moment came during the third game of the second set, which went to deuce seven times before Djokovic finally broke Caruso's serve.

As the game wore on, Djokovic appeared bothered by crowd noise, even though the Campo Centrale is empty of fans this year because of the coronavirus pandemic.

The only people inside the stadium were coaches and others working at the tournament.

"Which ones?" the umpire asked Djokovic, trying to figure out who was bothering him.

Djokovic replied curtly: "There's 10 people in the stands."

Djokovic, a four-time champion in Rome and chasing a record 36th ATP Masters 1000 title, next faces Italian qualifier Marco Cecchinato or Filip Krajinovic.

Nine-time Rome champion Rafael Nadal showed little signs of rust when he played his first match in 200 days as he beat fellow Spaniard Pablo Carreno Busta 6-1 6-1.

Nadal, who received a bye into the second round, has not played a tournament since winning his 85th singles title in Acapulco, having skipped the Western & Southern Open and the US Open in New York due to COVID-19 concerns.

The match was also Nadal's first on clay in 465 days after his French Open triumph last year and the 34-year-old Spaniard sent an ominous message to the field as he dominated the U.S. Open semi-finalist from start at an empty Foro Italico.

"It's good to be back on the Tour but obviously the feeling is not the best playing without crowds," Nadal said.

"At least there's one positive thing, the sport is back."

Also in the second round, Rome resident and fourth-seeded Matteo Berrettini defeated Argentina Federico Coria 7-5 6-1 while Marin Cilic beat sixth-seeded David Goffin 6-2 6-2.

Italian wildcard Jannik Sinner pulled off a stunning upset in the second round when he beat third seed Stefanos Tsitsipas 6-1 6-7 (11-9) 6-2 to take revenge on the Greek who beat him in straight sets at the same stage last year.

Sinner, 19, led 6-1 5-2 before Tsitsipas mounted a comeback and saved match points in the tiebreak, but Sinner clinched the decider as Tsitsipas racked up 58 unforced errors in the contest.

Sinner will next face Bulgarian Grigor Dimitrov, who eased past Yoshihito Nishioka 6-1 6-0.

Australian Associated Press