Seven-time grand slam winner Venus Williams overcame a player less than half her age on Monday in a vintage performance in the first round of the Auckland Classic.

Playing her first match in four months, the 42-year-old unearthed some trademark power to notch a first win in more than a year, adding another footnote to a professional career that has stretched into a 27th season.

An hour-long rain interruption worked in Williams' favour, as she resumed in style to beat fellow American Katie Volynets 7-6 (7/4), 6-2.

Volynets, who turned 21 on New Year's Eve, was leading the first set tiebreaker when play was suspended but she faded in a match that stretched late into the evening.

The former world No.1 is using this week to prepare for her 25th tilt at the Australian Open, having accepted a wildcard entry to the tournaments in Auckland and Melbourne.

She admitted the stoppage worked in her favour although it didn't feel that way at the time.

"It's hard when you're all fired up and just suddenly you have to stop," said Williams, whose previous match was a first-round loss at the US Open.

"I was so mad on the rain break. My coach could barely talk to me so I'm going to try to improve my attitude."

Williams has slipped outside the top 1,000 in the rankings but she showcased glimpses of her former class - and some creditable fitness - during the second set against 114th-ranked qualifier Volynets.

The tournament is being staged for the first time in three years, with the 2020 edition having been won by retired great Serena Williams -- Venus' younger sister.

Williams will face China's Zhu Lin in the second round, after she upset American sixth seed Madison Brengle 4-6, 7-6 (8/6), 6-4.

Third seed Canadian Leylah Fernandez notched a rapid win, dropping just 14 points in a 6-1, 6-1 defeat of 15-year-old Czech wildcard Brenda Fruhvirtova.

Top-seeded American and world No.7 Coco Gauff opens her campaign on Tuesday.

Also in action are three former Grand Slam winners - Briton Emma Raducanu and US pair Sloane Stephens and Sofia Kenin.