Daiya Seto Chasing Michael Phelps’s 400 IM WR: An Analysis

Earlier this month, Japanese swimmer Daiya Seto indicated his goal of breaking Michael Phelps world record in the 400 IM at this summer’s Tokyo Olympics. Phelps’s record of 4:03.84 was set at the 2008 Beijing Olympics. Approaching 13 years since that swim, it is the oldest men’s individual swimming record.

Seto, like Phelps, is a great all-around swimmer. His 1:52.53 in the 200 butterfly makes him the third fastest person of all time in the event. Two years ago he put a 59.79 in the 100 breaststroke. In 2016 he swam 1:59.50 in the 200 backstroke. And while he’s not known as a freestyle specialist, his best time of 1:47.71 was back in 2015. Seto definitely has the pedigree and strength in the individual strokes to make a run at the record. 

In light of his stated goals, I decided to take a look to see what it would actually take for Seto to break this record. We don’t want to just look at Phelps’s splits and say that Seto has to be faster than that. No, we want to take a look at how Seto swims his races and use that as a base for the splits he needs to target.

As a refresher, Phelps’s world record splits were the following:

Butterfly Backstroke Breaststroke Freestyle Total
54.92 1:01.57 1:10.56 56.79 4:03.84

Seto’s best time of 4:06.09 was swum in January 2020 and ranks him as the fifth fastest swimmer all-time in the event. His splits of that swim break-down as follows:

Butterfly Backstroke Breaststroke Freestyle Total
54.22 1:03.46 1:09.83 58.58 4:06.09

A quick comparison shows us that Seto’s splits on the fly and breaststroke were actually faster than Phelps’s WR splits. The breaststroke split isn’t surprising as that was Phelps’s slowest stroke relative to his other four. What is surprising is that Seto’s fly split is faster than Phelps considering at one point Phelps was the WR holder in both the 100 and 200 fly. 

Rather than just look at Phelps’s raw splits from his WR and say “that’s where Seto needs to be”, we can dig a bit more into the splits. We can take each stroke and look at it as a percentage of the overall time. For example, using Phelps’s fly split, 54.92 seconds/243.84 seconds = 22.52%. 

Butterfly Backstroke Breaststroke Freestyle
Split 54.92 1:01.57 1:10.56 56.79
Percentage 22.52 25.25 28.94 23.29

We can do the same thing with Seto’s 4:06 from last year:

Butterfly Backstroke Breaststroke Freestyle
Split 54.22 1:03.46 1:09.83 58.58
Percentage 22.03 25.79 28.38 23.80

We can also do the same for other swims from Seto, particularly those within the past two years:

Meet Time Butterfly Backstroke Breaststroke Freestyle
Sette Colli 2019 4:07.95 55.92








Worlds 2019 4:08.95 55.73








Japan Trials


4:09.02 55.47








We can confirm the trend where Seto is regularly faster on fly and breast than Phelps but Phelps is faster on back and free. With Phelps’s freestyle split being significantly faster than Seto’s, he will need to be well ahead of WR pace after the breaststroke.

Using the races and splits percentages, we can calculate the splits Seto would need based on the four races above:

Time Basis Butterfly Backstroke Breaststroke Freestyle Total
4:06.09 53.72 1:02.88 1:09.19 58.04 4:03.83
4:07.95 54.99 1:02.10 1:08.84 57.90 4:03.83
4:08.95 54.58 1:01.79 1:08.63 58.82 4:03.82
4:09.02 54.31 1:02.74 1:08.89 57.88 4:03.82

The numbers above show how truly impressive Phelps’s record is. There is a reason that the record has lasted almost 13 years — a swimmer needs to have a great combination of speed and endurance in all four strokes. Will Seto break Phelps’s last standing individual record? It will take a lot of work but at the Olympics in his home country, we’re saying there’s a chance.

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2 years ago

I think the 4:07.95 time basis (see above) with a much faster fly (54 low) and a slightly slower free (58 low) is his best bet.

tea rex
2 years ago

I remember Lochte/Phelps maxed out at around 1:08 breast split. I think Seto will need to be at least that to go 4:03.

2 years ago

Here are the splits for Seto’s WR possibility.

53+ for the fly, 1:01+ for the back, 1:08+ for the breast, and 57+ for the free.

There you have it for your scorecard for the Tokyo 400 IM final.

2 years ago

When you put the splits of Seto and Phelps next to each other, you can envision how a race between the two would play out.

They would be close after the fly and then Phelps would open a lead with the backstroke. Seto would close the gap on the breast and then Phelps would pull away for the win in the free.

In Tokyo Seto will need to be about two seconds ahead of the WR going into the free and then try to hang on. In an actual race he would have a gigantic lead over the field going into the freestyle. If that happens in Tokyo then you know the WR could be broken.

Reply to  Marklewis
2 years ago

Its funny because thats actually pretty much how it went when they raced in the scm 400im: https://www.youtube.com/watch?v=FTlVXnjHx7I&t=291s

2 years ago

Seto’s swimming deserves to be taken seriously. I think it’s unlikely he breaks the record, but he’s the only person in the world who can make a comment like this

Reply to  Penguin
2 years ago

Idk man hagino is still lurking in the shadows. Obviously not this year (out of shape comparatively and not competing in it regardless) but in a future world champs I could see him coming back possibly.

2 years ago

This article only made me appreciate Phelps greatness even more…I’m not sure when we are going to see another swimmer matching or exceeding his achievements. with more swimmers specializing in certain strokes it will be difficult for someone else to match his 2008 eight golds. The GOAT.

M d e
Reply to  Tomek
2 years ago

Dressel could win 7 this olympics with the addition of the mixed relay.

Reply to  M d e
2 years ago

He needs to match Phelps’ number of individual gold to be comparable.

Reply to  M d e
2 years ago

A hypothetical guy who wins four medals in a Games by swimming the 100 free plus three relays where he also swims the 100 free is not as impressive as a guy who wins four individual events at three different distances and different stroke disciplines.

Sprinters have more opportunities to medal, which is one of the reasons why I’m against stroke 50s at the Olympics. Give us an 800 medley relay.

2 years ago

Cool analysis. Even if it’s beyond his reach I appreciate that he’s public about his goal. That takes guts, and it is fun for us as fans.

Last edited 2 years ago by NONA
2 years ago

Seto is not breaking the WR. Like, he’s a good swimmer, but has never had that world-beating separation vs. his competition. He has never gotten close to a LC world record and only gets attention because the men’s IMs just aren’t that competitive right now.

Reply to  moonlight
2 years ago

I mean, he’s been half a second off the Phelps’ 200 fly record before milak had smashed it. I don’t think it’s actually impossible for Seto to break the 4IM record.

Mr Piano
Reply to  Arisuin
2 years ago

He was 0.5 off Phelps’s 2008 swim where he had his goggles filled with water. He was 1.02 off Phelps’s 2009 PR

There's no doubt that he's tightening up
Reply to  Mr Piano
2 years ago

Perhaps refering to MP’s textile best from 2007?

Reply to  moonlight
2 years ago

he won the 400 IM SCM by 5 seconds in the ISL finals. If he had had some competition in 2020 we wouldve seen the dominance.