She spoke just a minute after Williams had walked off the court at Arthur Ashe Stadium, for what is likely to be the final time as a pro. Tomljanovic had bested her in a three-hour epic match.
It was one of the biggest victories of her life, but there were no celebrations.
"I love Serena just as much as you do," Tomljanovic told the crowd, remembering how she'd idolized her growing up. "It's a surreal moment for me."
Williams had saved five match points until the sixth one ended her campaign. She had been building at the US Open, after winning her opening two matches against Danka Kovinic and world No. 2 Anett Kontaveit. Against Tomljanovic, she was the favorite -- for the first time in a match this tournament. There was a growing feeling that she could do the unthinkable and win the whole thing; the farewell tour was metamorphosing into the most incredible final last dance that only Serena Williams could craft.
But remarkable sports fairy tales are rare. And for every one of those unicorns, there are far more stories of dream narratives being ruined by reluctant protagonists.
"I feel like a villain," Tomljanovic said afterward.
She's not the first to feel like that, nor the last. Some of sport's greatest figures have been unable to finish their careers on a high note and it leaves a lingering impression on those who halted their heroes in the final steps.
Take Larry Holmes when he stopped Muhammad Ali in October 1980. Ali had come out of a yearlong retirement to take the fight with Holmes, but Ali was a shadow of his former self, and Holmes won conclusively with Ali's trainer Angelo Dundee stopping the fight in the 10th round. Holmes cried in his postfight interview. "When you fight a friend, to me a brother, you can't get happiness," Holmes said. "I fought a no-win situation." Ali would fight one more time, and lose.
There are the other sorts of great sports narratives where one old-timer manages to roll back the years to throw the younger generation off guard, only to fall short. There were those four memorable days at the 2009 Open where 59-year-old Tom Watson just missed out on the Claret Jug as he lost a 1-shot lead on the final day and then fell in a playoff to Stewart Cink.
Afterwards, Cink was asked whether he felt he had ruined the end of a Hollywood movie. "No, I don't feel that way. I feel like that whether Tom was 59 or 29, you know, he was one of the field, and I had to play against everybody on the field and the course to come out on top," Cink said. "I don't think anything can be taken away. Somebody may disagree with that, but it's going to be hard to convince me."
He added: "I don't feel ashamed. I don't feel disappointed. I'm pleased as punch that I've won this tournament."
And then there are the pre-planned farewells, like Serena's, where nostalgia and belief create a frenzy to all those watching, hoping to witness one last golden moment. Usain Bolt's farewell to the sport looked for all the world to be a guaranteed gold medal in the 100 meters at the 2017 World Championships in Athletics in London.
But instead, it was Justin Gatlin who came through for gold, with Bolt in third.
As Gatlin did his victory lap, he was booed by the crowd. "Bolt came to me after the race and said I didn't deserve all the boos from the crowd, and he's glad I've stayed classy," Gatlin said. "It's a surreal moment. He's going to be a figure that's widely missed, even by me."
Six days later, Bolt's hamstring gave out on the finishing straight of the men's 4x100. It would be his final act on the track -- the image of the fallen hero, his body giving out, only adding to the legend.
On Friday at Arthur Ashe, Tomljanovic's triumphs were met with silence, and then a crescendo of noise to try and rouse Williams. The victory took Tomljanovic 3 hours, 5 minutes, but was built on a lifetime of skill and mental strength. Every time she hit her first serve into the net, the fault was cheered. The one time her frustration boiled over and she spoke to the umpire about being interrupted by noise from the crowd, her irritation was met with boos.
To cope with having the vast majority of the 23,859 audience cheering for her opponent, she channeled Novak Djokovic's tactic. "When the crowd was against him, he just pretends it's for him," she said after her second-round win. "When they chant, I don't know, Rafa, Roger, whoever, he hears Novak, Novak. I kind of liked that response."
It worked for her. "I used that [tactic] and I also just really blocked it out as much as I could," Tomljanovic said after beating Williams. "It did get to me a few times internally. I mean, I didn't take it personally because, I mean, I would be cheering for Serena, too, if I wasn't playing her. But it was definitely not easy. There was no other way."
She formed her own "little bubble," and then after three sets of blistering tennis, she watched Williams' on-court interview and had a million emotions running through her.
"[It was] probably the most conflicted I've ever felt after a win," she said. "During the match I was so eager to win. But then when it ended, it almost didn't feel right. When she started talking about her family and everything, yeah, I got emotional because I can relate to having a strong bond with your family. When she said that she wouldn't be there if it wasn't for them, I relate to that a lot. The whole moment after was just tough to handle a little bit."
The crowd applauded after she spoke -- and it felt like the first cheers she had heard that night, barring the 15 or so people who sat in her box for the game.
On Sunday, Tomljanovic faces Liudmila Samsonova in the fourth round. It won't be back on Ashe, but instead on the next biggest show court -- Louis Armstrong. To get back on to Ashe, she'll have to keep winning.
Her greatest return in a Grand Slam to date is two quarterfinal exits at Wimbledon. She's overcome one monumental hurdle to try to better that.
But whatever happens here, she'll always have that honor of being the player to knock Williams out of her final US Open. And with that, she'll be the answer to one of sport's great trivia questions.
"I mean, no one's going to pronounce my name right," she said. "That's going to suck. But, I mean, I don't think I'd of been part of tennis history, so that's pretty cool. ... I really did want to play Serena before she retired.
"If I was the loser today I'd probably be really sad. I don't want to say I'm sad, but just conflicted a little bit."