While her ground strokes were erratic early on, Williams' serving was vastly superior to her 99th-ranked opponent, who dictated some rallies with her own power game but never came to grips with the conditions.

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Williams said playing a doubles match the previous evening with Caroline Wozniacki gave her an advantage against the Italian, who pushed her close at Wimbledon last year.

"I've always had really tough matches against Giorgi. The doubles really helped because got to come out here and play a little bit in these conditions and get used to them," Williams told Sky Sport NZ.

"It's really good to know that I still have some power left in my arm and my legs and everything. It felt really good."

World No.10 Williams moved well, although appeared to suffer a minor right ankle injury which prompted her to apply tape there early in the second set.

Day two of the tournament was free of any upsets.

Second seed Petra Martic of Croatia had to work hard to beat Usue Maitane Arconada 5-7 6-4 6-4, while third-seeded American Amanda Anisimova saw off Ukraine's Kateryna Kozlova in straight sets.

Scheduled to play in the evening session is fourth seed and two-time defending champion Julia Goerges of Germany, along with fifth seeded Dane Wozniacki.

AAP