Former world number one Venus Williams emerged from a back-and-forth battle with a 6-4, 0-6, 6-3 victory over German Andrea Petkovic to reach the second round at Indian Wells on Thursday.

The US veteran said she wasn’t feeling her best, and was at a loss for words to explain the win.

“I don’t know honestly. I’m still trying to figure it out,” said Williams, who closed out the first set after a visit from the trainer, before Petkovic had the second set all her own way.

Williams was broken as she served for the match at 5-2 in the third, wasting one match point.

Petkovic had a game point to extend the match before Williams broke her in the final game seal the victory.

“Every day is not your best day but that doesn’t mean the heart and desire aren’t there,” Williams said. “I’m just happy things went my way in the third set. It got really close there.

Williams was playing her first match since a third-round loss to then world number one Simona Halep at the Australian Open.

“I haven’t played in forever, so that was challenging in itself, to get back into competition,” said the 38-year-old who next faces third-seeded Czech Petra Kvitova – this year’s Australian Open runner-up.

France’s Kristina Mladenovic booked her second meeting in three weeks with world number one Naomi Osaka, beating China’s Zheng Saisai 7-5, 6-2 to reach the second round.

“It’s pretty funny, playing her back-to-back,” said Mladenovic, who toppled Osaka in Dubai in the Japanese star’s first match since winning the Australian Open.

“It’s going to be a brand new match,” Mladenovic said. “I’m sure her game suits well here as the defending champion, and I’m sure she wants to build on some wins again. I’m going to go out there confident, show a fight, and execute as well as I did a few weeks ago.”

In other first-round matches Thursday American Sam Querrey defeated Italian Matteo Berrettini 7-6 (7/5), 2-6, 6-4 to line up a meeting with 13th-seeded Milos Raonic – a rematch of their quarter-final here last year won by the Canadian.

Veteran Ivo Karlovic defeated Australian Matthew Ebden 7-6 (7/3), 7-6 (7/3) to line up an all-Croatian clash with 11th-seeded Borna Coric.

Canadian 18-year-old Felix Auger-Aliassime, ranked 58th in the world, defeated Britain’s Cameron Norrie 6-3, 6-2 to book a meeting with rising Greek star Stefanos Tsitsipas.

Serena Williams, also playing her first tournament since falling in the Australian Open quarter-finals, opens with a blockbuster second round match against another former world number one Victoria Azarenka.

Azarenka, now ranked 48th in the world, defeated Vera Lapko in straight sets on Wednesday to set up the clash that will highlight Friday’s night session.

Williams, seeded 10th, has won 17 of their 21 prior encounters but Azarenka won their most recent meeting – in the 2016 Indian Wells final. Since then both have become mothers, Serena to daughter Alexis Olympia and Azarenka to son Leo.

“It’s obviously going to be a really difficult match,” Azarenka said. “It’s not a second-round match for sure. But it’s going to be a huge challenge. We haven’t played for three years, we haven’t played since we both became moms, so it’s going to be a special one.”

All results

Men

1st rd

Bjorn Fratangelo (USA) bt Elias Ymer (SWE) 4-6, 6-2, 6-2

Philipp Kohlschreiber (GER) bt Pierre-Hugues Herbert (FRA) 6-4, 6-0

Albert Ramos (ESP) bt Damir Dzumhur (BIH) 6-1, 6-2

Ivo Karlovic (CRO) bt Matthew Ebden (AUS) 7-6 (7/3), 7-6 (7/3)

Prajnesh Gunneswaran (IND) bt Benoît Paire (FRA) 7-6 (7/5), 6-4

Jordan Thompson (AUS) bt Federico Del Bonis (ARG) 6-4, 6-7 (6/8), 7-6 (7/5)

Martin Klizan (SVK) bt Mischa Zverev (GER) 6-1, 6-4

Marcos Giron (USA) bt Jeremy Chardy (FRA) 7-6 (7/3), 7-6 (7/1)

Sam Querrey (USA) bt Matteo Berrettini (ITA) 7-6 (7/5), 2-6, 6-4

Felix Auger-Aliassime (CAN) bt Cameron Norrie (GBR) 6-3, 6-2

Yoshihito Nishioka (JPN) bt Denis Kudla (USA) 3-6, 6-3, 6-2

Guido Andreozzi (ARG) bt Ilya Ivashka (BLR) 7-6 (7/3), 6-4

Maximilian Marterer (GER) bt Ugo Humbert (FRA) 6-4, 6-2

Women

1st rd

Kristina Mladenovic (FRA) bt Zheng Saisai (CHN) 7-5, 6-2

Alison Van Uytvanck (BEL) bt Alison Riske (USA) 7-6 (7/1), 6-4

Ekaterina Alexandrova (RUS) bt Rebecca Peterson (SWE) 7-5, 3-6, 6-2

Madison Brengle (USA) bt Samantha Stosur (AUS) 6-2, 6-3

Monica Puig (PUR) bt Evgeniya Rodina (RUS) 6-0, 6-4

Misaki Doi (JPN) bt Ons Jabeur (TUN) 6-3, 6-3

Venus Williams (USA) bt Andrea Petkovic (GER) 6-4, 0-6, 6-3

Mona Barthel (GER) bt Zhu Lin (CHN) 6-4, 6-7 (4/7), 7-5

Kaia Kanepi (EST) bt Johanna Larsson (SWE) 6-2, 6-2

Ajla Tomljanovic (AUS) bt Alize Cornet (FRA) 7-5, 6-3

Natalia Vikhlyantseva (RUS) bt Priscilla Hon (AUS) 6-1, 6-1

Yulia Putintseva (KAZ) bt Timea Babos (HUN) 6-1, 6-3

With AFP inputs