Auckland - Former world number one Venus Williams battled into the second round of the Auckland Classic on Monday with a 6-3, 7-6 (7/1) win over Czech wildcard Andrea Hlavackova.
The seven-time Grand Slam champion began confidently but could not dominate Hlavackova, ranked 134 in the world, even though she never looked like losing the match.
"I knew it was going to be tough and I was really glad to close it out," she said.
Williams, now ranked 47, is seeking to rejoin the game's elite after two years marred by auto-immune disease and injury,
At 33, she is the oldest player at the Auckland tournament, a warm-up event for next month's Australian Open.
The American, who won her last Grand Slam in 2008, produced a mixed display in her first match of the season, committing 43 unforced errors in the 98-minute clash.
But her trademark booming serve clicked straight into gear as she fired down four aces, with her vast experience showing as she closed out the second set tie-breaker 7-1.
Williams will meet Austria's Yvonne Meusburger in the next round.
Earlier American Jamie Hampton, a semi-finalist in Auckland last year, struggled to overcome Austrian wildcard Tamira Paszek 1-6, 6-0, 6-3.
"It's the first match of the season and we're all shaking off a bit of rust," the fifth-seeded Hampton said.
Austria's Yvonne Meusburger ousted German seventh seed Mona Barthel 6-4, 6-3, while Spain's Garbine Muguruza celebrated her return from a long injury lay-off with a straight sets win over American Christina McHale.
"I was six months injured, so for me this was a great win," she said after the 6-4, 6-3 victory. "I don't feel pain in the ankle so I'm happy."
Top seed Roberta Vinci of Italy and Serbia's Ana Ivanovic, seeded second, will contest their first-round matches on Tuesday.
Results from day one of the Auckland Classic tournament on Monday (x denotes seed):
Venus Williams (USA) bt Andrea Hlavackova (CZE) 6-3, 7-6 (7/1)
Yvonne Meusburger (AUT) bt Mona Barthel (GER x7) 6-4, 6-3
Garbine Muguruza (ESP) bt Christina McHale (USA) 6-4, 6-3
Karolina Pliskova (CZE) bt Paula Ormaechea (ARG) 7-6 (7/2), 6-1
Kurumi Nara (JPN) bt Alexandra Cadantu (ROU) 6-1, 4-0 (retired)
Johanna Larsson (SWE) bt Lourdes Dominguez Lino (ESP) 7-5, 6-0
Jamie Hampton (USA x5) bt Tamira Paszek (AUT) 1-6, 6-0, 6-3