Serena Williams' shell-shocked reaction said it all. The American's post-match press conference, following her defeat in the Australian Open semi-finals to Naomi Osaka, was barely three minutes old before she dismissed herself while fighting back the tears. The overwhelming emotions may have been caused by another opportunity missed. Williams remains stuck on 23 Grand Slam singles titles, the most recent clinched just over four years ago at Melbourne Park when she was approximately six weeks pregnant. Since then, four major finals have come and gone in her pursuit of a record-equalling 24th, including the infamous defeat to Osaka in the 2018 US Open final which descended into chaos after Williams saw red, berated the umpire, and was deducted a game. Thursday inside Rod Laver Arena was a far less hostile occasion but one that proved no less heartbreaking for Williams. It all started so well, too. The 10th seed took advantage of a wayward start by Osaka to claim a 2-0 lead. Williams then had break and game points in the next three games and could conceivably have led 5-0. As it was, Osaka found her range and rhythm while the errors started to accumulate on Williams' racquet. Instead of holding a commanding lead, the American lost five straight games and never really recovered. After losing the first set and falling behind a break in the second, lesser players may have folded when faced with a rampant Osaka. Williams, of course, is not most players and she continued to fight. A break back to level the set at 4-4 gave her a glimmer of hope, but Osaka delivered an immediate response to break again, this time to love, before serving out the match with ease. "The difference today was errors," Williams said in her news conference. "Honestly, it was opportunities where I could have won. I could have been up 5-love. I just made so many errors. "Not like I was on the run or anything, they were just easy, easy mistakes. It was a big error day for me today." Williams looked genuinely exasperated with herself as she reflected on her performance, clearly feeling she lost the match more so than Osaka winning it. That, though, would be a disservice to Osaka who was outstanding and thoroughly deserved her 6-3, 6-4 victory. Perhaps then in addition to feelings of missed opportunity for Williams is a realisation that, at the age of 39 and with Osaka proving a formidable foe, her chances of capturing that historic major are fast diminishing. Williams has over the past few weeks played as well as she has at any time over the past four years and it simply wasn't good enough against a high-quality opponent. Williams' emotional press conference and her hand-on-heart farewell to the crowd led to speculation that this could have been the great champion's last hurrah in Melbourne. "I don't know, if I ever say farewell I wouldn't tell anyone," Williams said in response. Soon after, Williams made her tearful exit – from the room and from the tournament. It was almost symbolic that the player ushered in to replace her in the press conference room is the one who appears destined to succeed Williams as the biggest star in female tennis. The Japanese player's global appeal – as a world-class athlete, social activist, and amiable personality – has already seen her earnings skyrocket to make her the highest-paid female athlete in the world. Osaka may be friendly and personable off the court, but on it she is a different proposition. The 23-year-old is already a three-time Grand Slam champion and is the big favourite to add a fourth when she faces American Jennifer Brady on Saturday. "For me, I have this mentality that people don't remember the runners-up. You might, but the winner's name is the one that's engraved," said Osaka, who has gone on to win every Grand Slam title after reaching the quarter-final stage. "I think I fight the hardest in the finals. I think that's where you sort of set yourself apart." And set herself apart she has, just like Williams before her.