Osaka sacks second coach in seven months

Jermaine Jenkins replaced Sascha Bajin in February, just weeks after Osaka's Australian Open triumph. Kevork Djansezian/Getty Images

Two-time Grand Slam champion Naomi Osaka has sacked her second coach in seven months, splitting with Jermaine Jenkins in the wake of her disappointing US Open title defence.

Jenkins, a long-time hitting partner of Venus Williams, replaced Sascha Bajin in February, weeks after Osaka's Australian Open triumph.

"I'm super grateful for the time we spent together and the things I learned on and off the court, but I feel like now is an appropriate time for change," the Japanese 21-year-old wrote on Twitter.

"Appreciate you, forever warmed by you [...] Thank you for everything, it was a blast."

Former world No. 1 Osaka entered the US Open as top seed, but struggled with a knee problem before being upset by 13th seed Belinda Bencic in straight sets in the fourth round.

The loss was another disappointing moment in a difficult season for the power hitter since her second major title, with early exits at the French Open and Wimbledon.

The Australian Open win made the Japanese star Asia's first world No. 1 and the first player of any nation to claim their first two Slam titles back-to-back since Jennifer Capriati in 2001.

But after a first round exit from the Dubai Tennis Championships in Februrary, Osaka tearfully said the top ranking and accompanying attention were a heavy burden on her.

Australian Ashleigh Barty later took the No. 1 spot in the lead-up to Wimbledon, where Osaka said after her first-round exit the fun had gone out of her game.

As Barty faltered during the North American hardcourt season, Osaka reclaimed the top ranking in the lead-up to the US Open despite tepid form in Cincinnati and Toronto.

Her early exit from New York has seen her ranking slide to fourth, behind No. 1 Barty, Karolina Pliskova and Elina Svitolina.