INDIAN WELLS, CALIFORNIA (REUTERS, AFP) - Venus Williams fought back to down third seed Petra Kvitova 4-6, 7-5, 6-4 and reach the BNP Paribas Open third round on Saturday (March 9), while Naomi Osaka got her title defence off to a flying start with a straight-sets win over Kristina Mladenovic.
The Japanese world No. 1 beat Mladenovic 6-3, 6-4 - the win under the stadium court lights sweet revenge for the reigning US and Australian Open champion after she lost to the same opponent in the Dubai Tennis Championships first round last month.
She said it was the first time she had felt the pressure of defending a title.
"I've never been a defending champion before so I was pretty nervous and I'm glad I got the win," the 21-year-old said.
American Williams, 38, turned back the clock in the final two sets at Indian Wells, dialling up the speed on her first serves and playing stout defence to seal a win that looked unlikely when she was down a double break in the second set.
The seven-time Grand Slam champion threw her arms in the air and let out a roar when Kvitova sent a ball long on match point - the Czech's 56th unforced error of the day.
Williams tipped her hat to the two-time Wimbledon champion after the hard-fought contest.
"She has been playing so well and you never know what's going to come off her racket," a beaming Williams said in front of a fawning crowd as night fell on her native Southern California.
"I was just happy to have your energy to get pumped up. I just love the battle."
Men's world No. 1 Novak Djokovic, meanwhile, shook off a nervy start to dispatch US qualifier Bjorn Fratangelo 7-6 (7-5), 6-2 to reach the third round of the ATP Indian Wells Masters.
Playing his first match since winning a record seventh Australian Open title in January, the Serb was less than sharp in conceding an early break to his 128th-ranked rival.
He broke back as Fratangelo served for the set to knot it at 5-5, and then raced to a 4-1 lead in the tiebreaker. Djokovic had to dig deep, however, when Fratangelo battled back to lead 5-4.
After a double fault and a forehand error from the 25-year-old American, Djokovic suddenly had a set point, and once he'd pocketed the set, the second went all his way.
Admitted Djokovic, who is going for a record sixth Indian Wells title: "I didn't play my best. Credit to Bjorn for coming out firing from every corner.
"I was lucky to get the first set. After that, things went better for me."
After wrapping up the victory in one hour and 29 minutes, he loped over to share a word with US great Pete Sampras in the stands.
He next faces German Philipp Kohlschreiber, a 6-4, 6-4 winner over Australian Nick Kyrgios.
Earlier, another American Madison Keys blew a late lead to fall 3-6, 6-1, 7-5 to German Mona Barthel.
The 17th-seed had the match on her racket serving with a 5-4 lead in the third set but lost three straight games, including her final service game to love, allowing the unseeded Barthel to advance.
Next up for Barthel is a meeting with countrywoman Julia Gorges, who beat Estonian Kaia Kanepi 6-3 2-6 6-3 behind seven aces in an evening match.
Unheralded Russian Ekaterina Alexandrova upset former world No. 1 Caroline Wozniacki 7-5 2-6 7-5 in a battle that lasted nearly two and a half hours in the evening session.
The 24-year-old will face Belinda Bencic in the third round on Monday after the Swiss cruised to a 6-4 6-1 win earlier in the day.
Former world No. 1 Angelique Kerber was nearly perfect en route to a 6-0, 6-2 dismantling of Yulia Putintseva, winning 93 per cent of her first service points under sunny skies.
The eighth seed will meet red-hot Russian Natalia Vikhlyantseva in the third round after the qualifier crushed Spaniard Carla Suarez Navarro 6-2, 6-0.
Czech Karolina Pliskova, Latvian Anastasija Sevastova and Americans Danielle Collins and Christina McHale were among the other players who prevailed in their second-round matches.