Indian Wells - Former world No 1 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.
The 38-year-old next faces third-seeded Czech Petra Kvitova, this year's Australian Open runner-up.
Results on Thursday in the BNP Paribas Open WTA and ATP Masters hardcourt tournament (x-denotes seeded player):
Men
First round
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
First round
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
