Indian Wells champion Naomi Osaka defeated 23-times grand slam champion Serena Williams 6-3 6-2 in the Miami Open first round on Wednesday, the latest big win for the emerging 20-year-old Japanese player.

The pair were on serve in the first set of their first career meeting until Osaka forced break point chances at 3-3 and Williams was unable to deal with a blistering backhand at her feet.

The world No.22 broke Williams again after a back-and-forth deuce battle to take the first set.

Osaka’s powerful serving and relentless return game were even stronger in the second and she broke Williams to go 3-1 up and was never threatened again.

The match ended on an ugly unforced error by Williams, who hit a wide open forehand long to send Osaka into the second round, where she will face world No.4 Elina Svitolina of Ukraine.

“I was extremely nervous coming on to the court. I don’t know if anybody knows this but Serena is my favourite player,” Osaka said in an on-court interview.

“So just playing against her is kind of like a dream for me. I’m very grateful I was able to play her and it is even better that I was able to win.”

The 36-year-old Williams, playing her fourth match since the birth of her first child in September, is still working her way into form and although demonstrating her trademark power, she struggled to move smoothly around the court.

Osaka looked fresh despite having played seven matches in Indian Wells to capture her first career title on Sunday.

Williams has endured a first-round defeat only four other times, most recently at the 2012 French Open. The latest loss came at a tournament she has won a record eight times and considers her hometown event.

The match was the last for Williams at Key Biscayne, 140kms south of her home in Palm Beach Gardens, as the tournament is moving next year to the Miami Dolphins’ stadium.

Some felt it was unfair the Miami Open allowed Williams, an eight-times champion at the tournament, to play Osaka in the first round.

“Serena should have a special seeding, but also WTA should use the most current ranking,” tennis commentator and former world No.1 Lindsay Davenport said on the Tennis Channel.

“The men do it. It’s too big a tournament to have something like this happen.”

Osaka’s win over Williams was her latest victory over some of the biggest names in the sport.

She defeated former grand slam champion Maria Sharapova, fifth seed Karolina Pliskova and world No.1 Simona Halep in Indian Wells.