Since 2009, the prized 100-metres freestyle mark had belonged to Britta Steffan, the German who clocked 52.07s at the infamous supersuit worlds in 2009. Seven years had passed and still it withstood all comers.

That was until Campbell, in little more than a warm-up meet, coasted to the wall in 52.06s, stunning anyone watching and competitors around the world. And it looked hers to lower, as well, with none of her peers seemingly close enough to bend it further.

Enter Sarah Sjostrom, who obliterated the mark at the FINA world championships in Budapest in the wee hours of Monday morning (Australian time). Leading off Sweden's 4x100m freestyle relay, she touched the wall at 51.71s, making her the first woman in history to break 52 seconds.

To put that in context, Sjostrom finished with bronze in the 100m freestyle in Rio. If she had gone anywhere near her Budapest swim, she would have won by almost a full second.

It was a remarkable performance and a clear indication that while Budapest represents a partly experimental meet for the Australians, who are tinkering with their preparations after a tough meet in Rio, the big guns of world swimming have come to play.

Campbell would watch from the sidelines in Budapest after sitting out the meet, instead being part of the Swimming Australia support staff. If she could have picked anyone to steal a march on her time, outside of younger sister Bronte, it would likely have been Sjostrom.

The pair are friends and it was the Swede who comforted Campbell immediately after her disappointing performance in the Rio final, where she failed to medal after starting a prohibitive favourite. Now she represents Campbell's main rival at the top of the sprint ranks. If that can't get her fired up for a return, nothing will.

The Dolphins had some highly encouraging swims on day one in Budapest. Emma McKeon continues to set new marks of excellence, while the women's 4x100m relay managed to claim a tight silver despite missing the elder Campbell, the regular anchor in their world-record grouping.

Mack Horton wasn't able to replicate his 400m freestyle form, finishing second to arch-rival Sun Yang, but given he was one of the few Australians to step up under pressure in Rio, where he won gold, the Victorian has little reason for ongoing concern.

What day one did show was that if Australia are trying to catch up to the rest of the world, the rest of the world is stubbornly refusing to stand still. McKeon may be lowering her PBs - her 100m butterfly was an Australian and Commonwealth record - but Sjostrom stands firmly in her way.

Likewise in her pet 200m freestyle, where the unbeatable Katie Ledecky lies in wait. She may well go down as the greatest swimmer in history and no matter how fast McKeon goes, Ledecky always appears to have an extra gear casually up her sleeve.

Australia won eight golds in the Kazan event a year out from Rio, which as history shows doesn't always add up to much on the Olympic pool deck. This time, they may not win any, although Cameron McEvoy has as good a chance as anyone in the men's 100m freestyle.

New faces like Shayna Jack and Tasmanian 16-year-old Ariarne Titmus, who finished fourth behind Ledecky in the women's 400m freestyle, are emerging exactly at the right time. Now they will have no illusions as to what they are up against should they want to top a podium in Tokyo.

The the likes of McEvoy and defending world champion backstroker Emily Seebohm still to swim, the big guns of the Australian team need show they can produce their best at a major meet. It only took one day for the heavy hitters of global swimming to lift the bar even higher.