The first event of the first day of swimming prelims at the Tokyo Olympics produced what could end up being the biggest upset of the Games as Japanese swimmer Seto Daiya, the defending world champion in the men’s 400m individual medley, did not qualify to the final out of Saturday’s preliminary heats.

Seto was the consensus favorite in the event which requires swimming all four strokes for two lengths of the pool each. The Rio 2016 bronze medalist came into the Olympics with the fastest time of the year in the event at 4:09.02.

He went a full second and a half behind that pace Saturday, finishing fifth in the last of four preliminary heats. The time was only good enough for ninth overall; the top eight swimmers advance to the final.

Seto got out to an early lead, as expected, and turned at the 300-meter mark a full body length – 1.71 seconds – ahead of the pack. It all went wrong for the host nation’s star in the freestyle leg. Turning for the final length of the pool, Seto’s lead was reduced to just three tenths. He was helpless as the four swimmers to his immediate left and right all pulled ahead to qualify for the final.

Australia’s Brendon Smith won the heat in 4:09.27. American Jay Litherland and Italian Alberto Razzetti tied for the second spot.

The other American swimmer in the event, Chase Kalisz, also advanced to the final from the prior heat, going 4:09.65

Despite the catastrophic result in the 400 IM, Seto still has the 200m IM to make good on the opportunity to win a medal for Japan on home soil. He is the defending world champion in that event as well