2025 World Championships Previews: U.S. Women Reign Supreme in 4×100 Medley

2025 World Championships

• July 27 – August 3, 2025 (pool swimming)
• Singapore, Singapore
• World Aquatics Championships Arena
• LCM (50m)
• Meet Central
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• Live Results
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Women’s 400 Medley Relay: By the Numbers

• World Record: 3:49.63– United States (R. Smith, L. King, G. Walsh, T. Huske) (2024)
• World Junior Record: 3:58.38– Canada (T. Ruck, P. Oleksiak, R. Smith, K. Sanchez) (2017)
• World Championship Record: 3:50.40– United States (2019)
• 2023 World Champion: United States– 3:52.08
• 2024 Olympic Champion: United States– 3:49.63

The World Record breaking United States medley relay team has returned all four of their swimmers from the Paris Olympics, and they aren’t showing any signs of slowing down coming into Worlds, putting them in a league of their own for the final event of the meet.

How the event shakes out behind them is going to be the interesting part because it could go a number of different ways.

Three World Record Holders

The American women have three of the four 100 distance world record holders on the team this summer. The only swimmer they have who does not have the world record is Torri Huske on the freestyle leg, and only three swimmers at the meet have ever been faster than her in the event, Marrit Steenbergen from the Netherlands, who are likely not going to be a threat to the United States on this relay, fellow American Simone Manuel, who can’t swim against Torri on the freestyle leg, and Australia’s Mollie O’Callaghan.

Regan Smith is practically a lock for the backstroke leg, and she holds the 100 backstroke World Record in 57.13, which she set at last summer’s Olympic Trials. While she frequently finishes 2nd in the individual event to the Australian backstroker Kaylee McKeown, Smith finds another gear leading off this relay and almost never loses the leadoff leg of the women’s 4×100 medley relay, generally going faster than she did in the individual event.

Regan Smith (photo: Jack Spitser)

The butterfly leg is also all but a sure thing with Gretchen Walsh holding the World Record in 54.60 and her biggest in country competition coming from Torri Huske, who will likely swim the freestyle. Walsh split 55.03 on the relay in Paris, which was a few tenths faster than her lifetime best at the time, and was six tenths faster than her 55.63 from the Paris final. She is a very good relay swimmer, and even a few tenths drop from her World record would put the U.S. in very strong position.

Our final leg that we can be practically positive about is the freestyle. Torri Huske is one of the favorites to win the 100 freestyle, and she has some incredibly fast relay splits under her belt. In Paris, she split 52.42 to bring the World Record relay home, but she had two faster performances in the same meet. On the 400 free relay, she swam 52.06, and on the mixed 400 medley she was a blistering 51.88 for the win and another World Record.

The breaststroke leg is the one that is up in the air right now. Lilly King is the World Record holder in 1:04.13, but she hasn’t been that fast since 2019. She was on the relay in Paris, where she split 1:04.90. King has historically performed well on relays and last summer was no exception with her split being almost a full second faster than her individual swim of 1:05.60.

The ambiguity comes in with Kate Douglass and her recent strength in the 100 breast. At the United States Trials, she beat King, touching in 1:05.79 to earn her spot on the Worlds team in the event. This is the first time she will be swimming the 100 at a major international meet, which means that we don’t have any data for her potential split on the relay, but if she comes out ahead of King in the individual 100, she will take her spot.

Gretchen Walsh Regan Smith Lilly King Torri Huske (photo: Jack Spitser) (photo: Jack Spitser)

When we add the athletes together with their best times we get a blistering 3:48.15 time, which would completely shatter their World Record time of 3:49.63. King has not been that fast in recent years, which makes it hard to predict that she would have that caliber of swim again, but this would be her last race ever. If we increase her time to her fastest time in the last two years, the relay time would be 3:49.45, which is still under the World Record.

The final bit of math we will do is using their fastest relay splits from January 2024-Present. Despite being a smidge slower than the lifetime best relay, this time still comes in under the World Record at 3:49.09.

If we use the fastest configuration of splits, with fastest relay split or lifetime best, the relay drops to 3:47.74 with King’s 1:04.13 or 3:48.51 with her 1:04.90.

The Podium

In Paris, the same three women’s teams shared the podium in all three relays, and our predictions are not any different for this year’s Worlds.

Australia

Australia won the silver medal last summer, more than three seconds behind the United States, and while they still have some very strong swimmers, they don’t seem likely to climb the American mountain this year.

Kaylee McKeown is the fastest backstroker in the world right now. She won all three backstroke events at the 2023 World Championships, and won both backstroke events at the Olympics. In this relay, though, she has only touched ahead of Smith one time, and that was at the 2020 Olympics when she swam 58.01 to Smith’s 58.05. She also just scratched out of the 50 backstroke later this week, which doesn’t instill an exceptional amount of confidence in the rest of her backstroke races. She is always capable of something exceptional, though.

Australia’s weakest leg is their breaststroke, and that doesn’t seem likely to change this year. 16-year-old Sienna Toohey is their best breaststroker this year, coming in at 14th in the world with the 1:06.55 she swam at the Australian Trials. This is quite a bit faster than the 1:07.31 Jenna Strauch swam on the relay in Paris, and improves their time significantly. The biggest question surrounding Toohey is that this is her first big meet, and the 4×100 medley is at the end. Especially if McKeown is very close to Smith after the backstroke, the breaststroke leg would be a very high-pressure position for a 16-year-old. Toohey does have two breaststroke relay splits from the 2024 Junior Pan Pacs, her fastest being 1:08.05 which was about four tenths slower than the 1:07.68 she swam in the event prelims.

The fly leg will also see a new face with the retirement of Emma McKeon after the last Olympics. No worries for the Aussies, though as Alexandria Perkins has moved into the role smoothly, setting the 2nd fastest time in the world this year in the 100 fly with the 56.42 she swam at Australian Trials. This was more than a half-second drop from the 57.10 she swam at the 2024 Trials. It is just off the 56.25 that McKeon swam on the relay last year, but she will have a relay start to help. She swam the prelims of the relay in Paris, touching in 56.59 for the Aussies, which was about half-a-second faster than her lifetime best at the time.

Finally, they have Mollie O’Callaghan on the freestyle. O’Callaghan had the fastest split in the field on this leg in Paris, touching in 51.83 to grab the silver medal for Australia. O’Callaghan has a stacked schedule this week, and has been battling an injury, but she will likely swim very fast on this relay to bring the Australian’s home.

Mollie O’Callaghan (photo: Jack Spitser)

When adding their lifetime best flat start times together, the relay comes out to 3:52.38. If we change their flat starts to relay starts, the relay slows down to 3:54.19, since only O’Callaghan’s time is faster. If the athletes can match their best time on the relay, their time drops to 3:52.13 which is a second faster than they swam in Paris.

China

China earned the bronze in Paris, just a tenth behind the Aussie team in 3:53.23. They only lost one of their swimmers from Paris, and will be fighting with Australia for the silver.

Wan Letian swam the backstroke leg in Paris, where she split 59.81, which was about eight tenths off her lifetime best flat start time of 59.02. She has been 59.06 this year, which she did at the 2025 Spring Nationals, just off her lifetime best. She is not quite at the caliber of Smith and McKeown, but then not many people are.

China has incredibly strong middle legs, which is where they will do their best to catch Australia. Tang Qianting is their breaststroker, and her lifetime best of 1:04.39 has her as the favorite to win the 100 breaststroke later this week. She was 1:05.15 on the medley relay in Doha, which was her fastest relay split in the last 18 months. In Paris, she split 1:05.79. If she is able to drop into the 1:04 range on the relay split, that would be huge for China’s chances.

Zhang Yufei is the butterflier for China, and she had the 2nd fastest split in Paris, just behind Walsh, in 55.52. This is about a tenth faster than her lifetime best of 55.62, but is a second ahead of the Australian Perkins. She has not been as fast this season, coming in at 57.39 at the Chinese Nationals, but she will likely swim faster at Worlds.

Zhang Yufei (photo: Jack Spitser)

Their freestyle leg is where they are seeing a change from 2024. Yang Junxuan swam the relay last summer, but she is not swimming this year, opening up the spot for Wu Qingfeng. Yang anchored in 52.11, the 2nd fastest final split in the field. Qingfeng is only a touch slower than that time when looking at relay splits, anchoring China’s 4×100 freestyle relay in 52.31 in Paris. Her lifetime best flat start is only 53.23, but her flat start time doesn’t matter much when she has been that fast on the relay. Cheng Yujie could also get the nod for this spot, having a lifetime best flat start of 53.26 and split 52.76 in Paris. The freestyle relay will swim first, and it seems likely they will go with whoever has the faster split there.

When adding together their lifetime best times, the relay comes in at 3:52.26, which points to a potentially very exciting race between them and Australia. Their fastest relay start time is actually slower at 3:52.79, with Wan and Tang both having far slower relay starts than flat starts from the last year-and-a-half. If those relay splits drop to even match their flat start times, though, they could come in as fast as 3:51.24.

Just Off Pace

Canada was 4th last year, just outside of medal position in 3:53.91, but they lost one of their strongest swimmers and will likely struggle to get back there.

Canada’s Kylie Masse led off the Paris relay in 58.29, off her lifetime best of 57.70. She has been 58.18 this season and is a strong leadoff leg for the Canadian team. She was 4th in the individual event in Paris, and could realistically place the team in medal position going into the breaststroke leg.

Just like the Australian’s, breaststroke is where Canada struggles. Their fastest breaststroker this season is Alexanne Lepage, who was 1:06.87 at the Canadian Trials, a little off her lifetime best of 1:06.58. Lepage missed the Olympic team in the event last year, but she swam a medley relay at the end of July, splitting 1:06.87 on the breaststroke leg, which was about three tenths slower than the 1:06.54 that Sophie Angus split in Paris. Angus is on the team again this year, and could end up in the final, though Canada will need to be much faster than 1:06.5 if they want to contend with China and Australia.

On the fly leg, Canada lost National Record butterflier Maggie MacNeil to retirement after Paris. MacNeil was 55.79 on the fly leg to keep Canada in contention, and they don’t have anyone who has been close to that this season. They could sub Summer McIntosh into that spot, where she normally swims freestyle, but we have no basis for what McIntosh could do on this leg of the relay. Her lifetime best is 57.19 from April of 2024, but she could easily be far faster than that.

Summer McIntosh (photo: Jack Spitser)

If they don’t put McIntosh on the fly leg, opting to keep her on freestyle, where she is also needed, their next best flyer is Mary-Sophie Harvey who has a lifetime best of 57.31, but has only been 58.19 this season. In Paris, she swam the fly leg in the prelims, where she split 57.68.

I think that it is more likely they use McIntosh on the fly and Harvey on the freestyle leg, since their times are closer. In Paris, McIntosh anchored Canada’s relay in 53.29, the 5th fastest split in the field. Sophie-Harvey has the 2nd fastest 100 freestyle time in Canada this year, after Penny Oleksiak who is provisionally suspended, in 54.34. Her lifetime best stands at 53.71 from the Canadian Trials last May. It’s a bit slower than McIntosh’s relay split, but they don’t have an exceptional amount of options.

We don’t have recent relay splits for McIntosh on fly or for Harvey on freestyle, so we will have to use their flat start times for the math when adding together the lifetime bests, but you can use your imagination for what they could do from a relay start. Looking at lifetime best times for everyone, the relay comes out to 3:55.18. When those get changed to relay splits, the relay slows down to 3:56.06, partially because we don’t have a split for McIntosh. These times are very far off the 3:53.91 they swam in Paris, and while McIntosh can likely go faster, they need more than just the two-to-three seconds she would give them.

Other Contenders

Japan

They were 5th last year in 3:56.17, and while they have the potential to be faster, their athletes would need to tap into speed they haven’t seen in years. Rio Shirai, the backstroker, split 1:01.24 in the Paris final, but has a lifetime best of 59.43 from 2019. The freestyler, Rikako Ikee is a similar story, with her splitting 53.58 with a lifetime best of 52.79 from 2018. If all of the swimmers can even match their best times, their time would add up to 3:54.46, which would put them in a good position to finish ahead of Canada.

France

The French lost their backstroker and breaststroker between the Olympics and now. Backstroker Emma Terebo will be replaced by either Pauline Mahieu or Mary-Ambre Moluh, who are only coming in about a tenth behind the 59.00 she split in Paris. They do not have an athlete entered in any of the women’s breaststroke events at the Championships, but Cyrielle Duhamel was the fastest Frenchwoman at the French Elite Championships in June in 1:08.14, and she is on the roster for the IM events so she will likely take over, though she is a little more than a second slower than Bonnet was. Lilou Ressencourt will take over fly duties and Beryl Gastaldello returns for the freestyle. They won’t contend for a medal, but they should comfortably be in the final.

Netherlands

World Aquatics Championships – Doha 2024
02 – 18 Feb 2024
credit Fabio Cetti

The Netherlands were 8th last year, and they lost breaststroker Tes Schouten. They will have to battle to end up in the final, which could be especially hard if they don’t use Marrit Steenbergen on the prelims of the relay, without her they could end up out of the final entirely, but with her they are likely finalists.

Germany

The German team was 9th last year, about half-a-second out of finals position, but Sweden lost Sjostrom on the end of their relay which opens up the door for another team to swoop in. They have some of the top swimmers, especially in Anna Elendt’s 100 breaststroke and Angelina Koehler’s 100 fly. If the backstroke and fly can drop time from Paris, they can take advantage of Sweden’s loss.

Great Britain

Great Britain was 10th last year, just two tenths back of Germany, and they will also be hoping to take advantage of Sjostrom’s absence. They are perhaps an even stronger relay than Germany this year, with Angharad Evans having some huge swims in the breaststroke events which can help propel them up the leaderboard if she recreates them. They did lose their backstroker Kathleen Dawson, but they have Lauren Cox entered in the 50 backstroke, and she has been 59.60 in the 100, which is faster than the 1:00.67 Dawson swam in Paris.

The Picks

The podium is very clear cut in this race. The biggest challenge is determining which team will finish 2nd.

Australia has some young talent, and I think it is hard to look away from their two athletes on the ends. China is the opposite, with the middle 100 being their strongest, but they will need a sizable lead to hold off Mollie O’Callaghan on the end.

I am giving the silver to the Aussies, but I would not be surprised no matter who ends up taking it.

Dark Horse: Russia/NAB- I have said it before, but it is so hard to predict how the NAB athletes will finish because it has been six years since they had a full contingent at a long course Worlds meet. They have some very strong athletes in Evgenia Chikunova and Daria Klepikova, but they don’t have any backstrokers who have been under a minute this year, and Klepikova is their fastest freestyler and flyer which makes it hard to figure out what they will do. I could see a world where they finish in the top-half of the final, or where they miss it entirely.