INDIAN WELLS, California - Novak Djokovic was shocked by Botic van de Zandschulp 6-2 3-6 6-1 in the second round of Indian Wells on Saturday as the Serbian suffered an early exit at the hands of a tournament lucky loser for a second consecutive year.

Djokovic fell to lucky loser Luca Nardi of Italy in the California desert last year and history repeated itself on Stadium One court a day after top seed Alexander Zverev also went out.

The twenty-four time Grand Slam champion got off to a horrid start, hitting 14 unforced errors and being broken twice in the opening set.

He regrouped to race out to a 3-0 lead in the second, levelling the contest with a mighty forehand winner and pumping his fist in front of the packed, sun-soaked crowd.

But giant killer van de Zandschulp ran away with the decider, breaking Djokovic for a fourth time with a perfectly executed lob for a 3-1 lead and sealing the stunning upset when Djokovic's shot went wide on match point.

"I started really well and then of course Novak came back," said van de Zandschulp, who secured a berth to the tournament upon the withdrawal of 47th ranked Facundo Diaz Acosta.

"In the end I was happy to get my level back."

Van de Zandschulp was up a set and 3-0 on Nick Kyrgios in his first-round match on Stadium One on Thursday before the Australian withdrew with wrist pain.

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Djokovic, 37, retired from his Australian Open semifinal against Alexander Zverev with a hamstring injury and lost in the Qatar Open first round last month.

He said the leg injury was behind him coming into the tournament and did not look hampered by it in his match of Saturday, where he was accompanied by coach Andy Murray.

"No excuses for a poor performance," Djokovic said.

"It doesn't feel great when you play this way on the court, but congratulations to my opponent.

"Just a bad day in the office."

Djokovic's loss led a day of upsets that included seventh seed Andrey Rublev losing 6-4 7-5 to Italy's Matteo Arnaldi and 17th seed Felix Auger Aliassime falling to American Jenson Brooksby 6-4 6-2.

World number one Jannik Sinner is not playing at the tournament as he serves a doping suspension.

Keys and Alcaraz cruise

Earlier, Australian Open champion Madison Keys crushed Anastasia Potapova 6-3 6-0 in her first match as a Grand Slam champion, while Carlos Alcaraz began his bid for an Indian Wells three-peat with a 6-4 6-2 win over Quentin Halys.

Alcaraz is looking to join tennis greats Novak Djokovic and Roger Federer as the only players to have triumphed three successive times in "Tennis Paradise".

"I couldn't wait to start the tournament, to get here again," the Spaniard said after dispatching his French opponent.

"Outside my country, this is my favourite tournament by far. It's a privilege."

Alcaraz will play Canadian Denis Shapovalov in the third round.

Twelve months ago, a swarm of bees on Stadium One court stung Alcaraz and suspended play for nearly two hours during his quarterfinal.

Lance Davis of Killer Bee Live Removal played the hero that day, removing the bees from a moving camera over the court without harming them, and Alcaraz and Davis met at the net before Saturday's match where they shook hands and shared a laugh.

While Alcaraz is already a four-time major champion at the age of 21, Keys had to wait a few weeks shy of her 30th birthday before finally joining that exclusive club in Melbourne and that success seems to have energized her.

Keys broke Russian Potapova's serve for a third time to clinch the first set and rolled through the one-sided second set to extend her winning streak to 13 matches.

"I'm so happy to be here," Keys said in an interview on centre court.

"Australia was obviously an amazing moment so it's really nice to be playing at home for my first tournament back at a place I've played at so many times in front of some amazing people."

Next up for world number five Keys is a third-round meeting with either 28th seed Elise Mertens or Kimberly Birrell of Australia, who play later on Saturday.

Sabalenka powers through

Top seed Aryna Sabalenka was tested but ultimately prevailed over young American McCartney Kessler 6-7(4) 6-3 under the lights.

The Belarusian was in full command of her formidable serve and never faced a break point while crushing six aces and winning 90 percent of her first serve points.

She sealed the win with a pair of deft backhand volleys on match point to set up a meeting with Italian Lucia Bronzetti.

American Taylor Fritz, who lifted the trophy here three years ago, struggled to close out Italian Matteo Gigante but ultimately prevailed 6-3 7-5 in front of a full house on Stadium Two court.

Fritz was unable to serve out the match at 5-4 in the second set but broke back in the next game en route to the finish.

The third seed said he was being patient with himself as he was coming off an abdominal injury he suffered right after the Australian Open that kept him out of the tournament in Acapulco last month.

"There's definitely things I could have done better in the match but overall it was a pretty solid match," he said.

"I can't expect to come back and play perfect tennis. I've been injured, so I didn't have ideal prep coming into the tournament."

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Fritz will face 30th-seeded Chilean Alejandro Tabilo for a spot in the round of 16.