It's probably time to admit we all got a little bit too used to celebrating Australian gold at these Olympics so far.

How can you tell? When we sit down to watch the men's and women's 100m freestyle finals and feel just the tiniest pang of disappointment that Kyle Chalmers could only take silver, and that Mollie O'Callaghan and Shayna Jack missed out completely.

We've been spoiled, no doubt about it. But on a night in which exceptional performances still weren't enough for medals, disappointment would probably be displaced.

Chalmers, for one, came second to the fastest time any human had ever swum in 100m. China's Zhanle Pan broke his own world record by an astonishing 0.40 seconds, and finished 1.08 seconds ahead of Chalmers.

There was, unfortunately, no beating that.

But for Chalmers to medal in this event now across three Games — gold in Rio, silver in Tokyo and Paris — elevates him to the very highest tier of Australian swimmer. Longevity in such a physically demanding event is not something to sneeze at.

Chalmers's preparation had been impacted by a back issue in recent months, one that he has been dealing with on and off for at least five years.

At the trials in June, he told a story of how he spent a couple of days labouring as a landscaper on the Sunshine Coast. That sort of taxing physical work wasn't an issue for his back, but the day off on the couch he afforded himself afterwards did.

It was rest, not painstaking work, he wasn't used to.

His back locked up to such an extent that he nearly missed the Olympic trials altogether, rescued only by an inundation of cortisone shots on competition day.

Chalmers said in the build-up to this final his back was "the best I could possibly get it", which could mean any number of things. What he must have known though was that in a field this tight and a race this quick, any slight hindrance would would be enough to take him out of contention.

He certainly didn't seem hindered. Slow out of the blocks, Chalmers found himself in a not uncomfortable position well back at the turn.

He was always going to mow down most of the field, as is his forever impressive way, but this time one man from China was simply too far ahead.

The pace of the men's final stood in stark contrast to the women's earlier in the night, a race that had promised so much for Australia but ended cruelly.

The last time O'Callaghan took to this pool for a final it finished with her sharing the podium with an Australian teammate.

On Thursday morning, there were realistic expectations that the dose could be repeated, with Jack taking the place of Ariarne Titmus. Jack had qualified for the final second fastest, with O'Callaghan only marginally behind in third.

The pair are sprint specialists and thrive in the chaos of the up-and-back 100m race. But you can only ever be so good at a race in which there are so many variables packed into such a short stretch.

Winners from wider lanes are not uncommon, and the slightest missed stroke or split second delay on the blocks are generally the difference.

As Jack said earlier in the week after her 100m heat, "it's not necessarily about doing your best, it's actually about being the best on the day".

On this day, Sarah Sjöström was the best. She was fourth at the turn but hit her stride in the final 50, sneaking ahead of American Torri Huske by 0.13 seconds.

Sjöström's time was well short of the Olympic record set by Emma McKeon in Tokyo, and even further behind her own world record, incredibly set in 2017 when Sjöström was 23.

The winning time of 52.16 is the exact same as O'Callaghan's winning time from the 2023 World Championships. In fourth place, she was 0.01 seconds off a bronze medal — which, knowing Mollie, would have only been a consolation anyway.

Maybe she lost a bit of rhythm in the final few metres and missed her touch by that critical split second. Maybe, given she hit the turn in seventh place, she started too slowly and left herself too much to do.

Whatever the cause, O'Callaghan was left smarting. While Jack took a moment poolside to wave to her family and smile, no doubt reflecting on the unbelievable journey that has taken her to an individual final at the Olympic Games, O'Callaghan was off like a flash.

She will suit up for at least one more crack at gold in Australia's imperious 4x200m freestyle relay team, but the reigning world champ clearly was understandably disappointed at the result.

"I expected a lot more," O'Callaghan said.

"But at the end of the day you've got to suck it up and wait another four years."

O'Callaghan will definitely see another Olympic campaign, and Jack may well too, but this will most likely be Chalmers's Olympic swan song.

He has been titanic in the green and gold, a master of the most unpredictable of races. He has suffered setbacks and disappointment through his career but has always found a way to bounce back.

He is example for all of Australia's rising swimmers to follow, not just his young teammates left licking their wounds after a night that didn't quite go as planned.