NEW YORK: Serena Williams bowed out of the US Open and headed into retirement on Friday after a battling loss to Australia’s Ajla Tomljanovic.

On another night of searing emotion in the Billie Jean King Tennis Center’s main Arthur Ashe Stadium, 23-time Grand Slam champion Williams finally met her match in Tomljanovic, losing 7-5, 6-7 (4/7) 6-1 in an attritional slug-fest lasting more than three hours.

The defeat was almost certainly Williams’ last ever appearance in a Grand Slam singles event, the final act of a 27-year professional career that saw the 40-year-old American become a sporting and cultural icon who many believe is the greatest women’s tennis player in history.

“It’s been a fun ride,” a clearly emotional Williams said in an on-court interview following her loss.

“It’s been the most incredible ride and the journey I’ve ever been on, I mean, in my life.

“I’m just so grateful to every single person that’s ever said, ‘Go, Serena,’ in their life. You got me here.”

Although Williams has not definitively announced her retirement, she said in a Vogue magazine essay last month that she would “evolve” away from tennis after the US Open.

Williams said Friday that she was excited by the prospect of her life after tennis.

“I’m ready to, like, be a mom, explore a different version of Serena,” she said.

“Technically in the world, I’m still super young, so I want to have a little bit of a life while I’m still walking.”

Golf superstar Tiger Woods and former US first lady Michelle Obama were among a legion of admirers who paid tribute to Williams following her US Open exit.

“[Serena Williams] you’re literally the greatest on and off the court,” tweeted Woods.

“Thank you for inspiring all of us to pursue our dreams.”

Obama meanwhile saluted Williams’ rise from the gritty Los Angeles neighbourhood of Compton to the pinnacle of her sport.

“Congrats on amazing career, [Serena Williams]! How lucky were we to be able to watch a young girl from Compton grow up to become one of the greatest athletes of all time,” tweeted Obama.

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