NEW YORK -- Serena Williams gave an emotional speech after what was likely her final tennis match Friday night, an over-three-hour 7-5, 6-7 (4), 6-1 loss to Ajla Tomljanovic in the third round of the US Open.

"Thank you daddy, I know you're watching. Thanks mom," Williams said before starting to cry during her postmatch on-court interview with ESPN's Mary Joe Fernandez. "Everyone that's here, that's been on my side, for so many years, decades ...

"These are happy tears, I guess. I don't know. And I wouldn't be Serena if there wasn't Venus, so thank you Venus. She's the only reason Serena Williams ever existed ... It's been a fun ride. It's been the most incredible ride and journey I've ever been on."

Williams, 40, first mentioned her impending farewell to the sport in a Vogue essay posted during the Canadian Open last month, citing her desire to have another child. In the piece, she said she preferred the word "evolution" instead of "retirement" and acknowledged how difficult it was to come to the decision.

During her news conference after the match, Williams told reporters she was excited about spending more time with her daughter, and "explore a different version of Serena." However, she didn't completely close the door on a future comeback.

When Fernandez asked her if there was any chance she would reconsider walking away, she smiled. "I don't think so, but you never know."

A little later, pressed on the same topic at her postmatch news conference, Williams joked, "I always did love Australia,'' the country that hosts the next Grand Slam tournament in January.

Since her announcement, Williams has been given a hero's farewell from the crowds in Toronto, Cincinnati and New York. All three of her matches helped break US Open attendance records and included everyone from former President Bill Clinton to Tiger Woods. Even her doubles match with sister Venus was played on Ashe on Thursday night to a capacity crowd.

Williams' practice session Friday drew thousands, just hoping to catch a glimpse. The fervor around Williams even resulted in ESPN bumping the Michigan State-Western Michigan college football game to ESPN2 in order to move Williams' match to the primary channel.

Williams' career was celebrated following her first-round match with an on-court ceremony hosted by Gayle King and featured a video narrated by Oprah Winfrey and a tribute from Billie Jean King.

"Thank you for showing us what it means to come back and for never, ever backing down," Winfrey said. "Thank you for changing the face of the game, for inspiring the next generation. Thank you for thinking outside the lines and encouraging us to evolve. Thank you for showing us how to love the sport, and for always loving us back."

Aside from her interview with Fernandez, there was no formal ceremony after the match Friday, but the crowd -- which included Spike Lee, Gayle King, Stan Smith, Saquon Barkley, Russell Wilson, Ciara, Bella Hadid, P.K. Subban and Venus -- showered her with ovations throughout, including multiple "Se-re-na" chants. Despite their collective passion and obvious admiration, it wasn't enough to propel Williams to another victory.

After dropping the first set, a decider looked all but guaranteed after Williams won the first four games of the second set, but Tomljanovic and her powerful forehand relentlessly fought back. She staved off four set points in the nine-deuce eighth game of the set. Ultimately, after an intense tiebreak, Williams forced a third set.

But she had little left for the decider and struggled with her movement. After breaking Tomljanovic in the opening game, the Australian won the next six games to clinch the match. Williams, however, fought until the end, and Tomljanovic needed six match points to prevail.

"I've been down before. ... I don't really give up,'' Williams said. "In my career, I've never given up. In matches, I don't give up. Definitely wasn't giving up tonight.''

Tomljanovic said she wasn't surprised by Williams' fight until the end. "She's Serena," Tomljanovic said during her own on-court interview. "That's just who she is, and she's the greatest of all time. Period."

Tomljanovic is unabashedly a fan of Williams, having grown up watching her play on TV.

"I'm feeling really sorry, just because I love Serena just as much as you guys do," said Tomljanovic, who has never been past the quarterfinals at any major. "And what she's done for me, for the sport of tennis, is incredible. This is a surreal moment for me.''

Then, drawing laughs, Tomljanovic added: "I just thought she would beat me. ... She's Serena. That's that's just who she is: She's the greatest of all time. Period."

After congratulating her opponent, Williams waved to the crowd and briefly covered her tearful face with a towel before doing her interview. As Williams stepped off the court for the final time in singles play at Arthur Ashe Stadium, as Tina Turner's "Simply The Best" played, it marked the possible end of a 27-year career that transcended the sport and made her a global superstar.

Williams' mark of 23 major titles is the most by any player in the Open Era and trails only Margaret Court (24) for the most ever. Her lengthy list of accomplishments includes 73 career singles titles, 16 major doubles and mixed doubles titles, 4 Olympic gold medals and 319 weeks at No. 1.

She owns various records, including the most hard-court major titles (13) by any player, the most Grand Slam victories (367) by a woman and is tied with Chris Evert for the most US Open singles titles (6) in the Open Era. Williams is one of four tennis players in the Open Era to record a singles titles in four different decades. At 35, she became the oldest woman to win a major and hold the No. 1 ranking.

Williams also made her mark off of the court since bursting onto the scene. A longtime member of the WTA's Player Council, she advocated for equal prize money for women alongside Venus, and has become an advocate for equality and social justice.

"It's been a long time. I've been playing tennis my whole life,'' Williams said Friday night, after performing one last twirl-and-wave move usually reserved for victories. "It is a little soon, but I'm also happy because, I mean, this is what I wanted, what I want.''

The Associated Press contributed to this story.