Kiwi track cyclist Shane Archbold watched his Olympic medal hopes disappear with two disastrous performances in the omnium today - a puncture in the 4000m individual pursuit and a weak 13th in the 15km scratch race.
The Timaru 23-year-old was halfway through the pursuit - the fourth event of the omnium - when his rear tyre deflated. He was on track for a good time and well ahead of his Argentinian rival Walter Fernando Perez, before raising his arm once he became aware of the issue.
He was forced to ride by himself at the end of the programme 20 minutes after his aborted effort and eventually registered the sixth fastest time of 4m 26.581s, after effectively racing 6000m.
He entered the scratch race in seventh place on 29 points, but was lapped by the frontrunners to slip back a place in the standings.
Dane Lasse Norman Hansen recovered from a mid-race crash to snatch the lead overall with the same points (25) as second-placed Elia Viviani of Italy and Frenchman Bryan Coquard.
Meanwhile, in the women's sprint, Natasha Hansen progressed through to the 1/8 finals, losing her 1/16 race against Ukraine's Lyubov Shulika, but defeating her two opponents in the three-way repechage.
She then lost to Chinese Shuang Guo and finally fell out of medal contention when she trailled home third in her three-way 1/8 repechage. Hansen will now race for minor placings.
Britain's Victoria Pendleton set a new world record of 10.724 to qualify fastest.