Djokovic dispatches Fratangelo

World number one Novak Djokovic shook off a nervy start to dispatch US qualifier Bjorn Fratangelo in straight sets on Saturday to reach the third round of the ATP Indian Wells Masters.

Djokovic, playing his first match since winning a record seventh Australian Open title in January, 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 the tiebreaker 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.

Djokovic next faces German Philipp Kohlschreiber, a 6-4, 6-4 winner over Australian Nick Kyrgios.

Kyrgios, seeded 31st, was coming off a scintillating run to the Mexico Open title in Acapulco, where he defeated Nadal, ninth-ranked John Isner and, in the final, third-ranked German Alexander Zverev.

Third-seeded Zverev advanced when Slovakian foe Martin Klizan retired with an ankle injury with the German leading 6-3, 2-0.

Action opened on stadium court with 18-year-old Canadian Felix Auger-Aliassime powering past Greece's Stefanos Tsitsipas, 6-4, 6-2, for his first win over a top-10 player.

Auger-Aliassime, who next faces Japan's Yoshihito Nishioka, is one of four teens in the draw, along with countryman Denis Shapovalov, Alexei Popyrin and lucky loser Miomir Kecmanovic.

Kecmanovic gained entry into the second round in place of injured fifth-seed Kevin Anderson.

He made the most of his chance, beating Germany's Maximilian Marterer, 6-3, 6-2, to reach the third round.

At the other end of the age spectrum, 40-year-old Ivo Karlovic advanced with a 6-4, 7-6 (7/4) victory over 11th-seeded Croatian Borna Coric.

Venus topples Kvitova

World number one Naomi Osaka launched her Indian Wells WTA title defence with a 6-3, 6-4 victory against Kristina Mladenovic on Saturday.

Osaka booked a third-round meeting with American Danielle Collins, a 6-4, 6-1 winner over Kirsten Flipkens.

Seven-time Grand Slam champion Venus Williams pulled off the upset of the day, rallying from a set and two breaks down to topple third-seeded Petra Kvitova 4-6, 7-5, 6-4.

Caroline Wozniacki, the 2011 winner, fell 7-5, 2-6, 7-5 to 59th-ranked Russian Ekaterina Alexandrova.

Elsewhere on Saturday, fifth-seeded Karolina Pliskova shook off a slow start to defeat Japanese qualifier Misaki Doi 6-7 (4/7), 6-1, 6-1.

Pliskova next faces another qualifier, Belgian Ysaline Bonaventure, who defeated 28th-seeded Donna Vekic of Croatia 1-6, 7-6 (7/5), 6-4.

Eighth-seeded German Angelique Kerber eased into the third round with a 6-0, 6-2 victory over Kazakhstan's Yulia Putintseva.