Matteo Berrettini has effortlessly beaten Roberto Carballes Baena in the rain sodden Napoli Cup, reaching the quarter-finals and redeeming himself after last week's loss in Florence.

Only eight days after Spain's Carballes Baena had triumphed over the Italian on the indoor courts in Florence, Berrettini took just 91 minutes on Thursday to win 6-4 6-2 on the outdoor courts in Naples in front of an impassioned home crowd.

"The atmosphere, the conditions (were different to Florence) for sure," Berrettini said.

"This is outdoor, way warmer, and I wanted to get revenge.

"I felt like I had a lot of chances last week and it was tough to digest, especially because I played in Florence, in Italy, so it was really tough. 

"But today I stepped on the court, I think with even more will to win this match, and I think I played better."

Berrettini will next compete against Taro Daniel, after the Japanese beat Pedro Cachin 6-4 7-6 (7-2).

Mackenzie McDonald, of the United States, upset third-seeded Roberto Bautista Agut 6-4 6-4 in the second round, mere hours after also eliminating Francesco Passaro in the delayed tournament.

Several players had to pull double duty on Thursday as the start of the singles main draw had been postponed by two days from Monday because of multiple issues with the playing surface.

Players had threatened to boycott the event, and play was also stopped early on Wednesday when it finally got underway because of humidity and slippery conditions on the courts situated next to the bay.

Chinese qualifier Zhang Zhizhen started off by completing his 6-4 7-6 (10-8) victory over Marton Fucsovics before returning to see off sixth-seeded Sebastian Baez 7-6 (7-5) 7-6 (13-11) to leave him on the verge of becoming the first Chinese player to break into the top 100 next week.

―With AAP.