[UPDATED 950pm with Schooling reax]
A last-minute change in swim cap and goggles ended up causing Singapore's Joseph Schooling to lose focus and be way off his best.
Swimming in lane 8, Schooling finished last in the 200m butterfly heats at the Aquatic Centre in London on Monday afternoon.
The 17-year-old, who currently attends and trains at the Bolles School in the USA, failed to advance to the last 16 in his first appearance at the Games.
Explaining his disappointing performance, Schooling (@joschooling) tweeted moments after his race, "Disappointed with my swim. Right before I had to swim the officials tell me I can't use TYR... This is absolute BS thanks for messing my swim."
It turned out that an official had told Schooling just before the race that his brand of goggles and cap were not approved, leaving him to scramble for replacements just five minutes before the start of the race.
Jessie Phua, Chef-de-Mission for Team Singapore at the London Olympics, told reporters after the swim that she was very upset that this has happened. She promised that an internal investigation will be conducted to find out what happened and would not want to add anything more than that."
May Schooling, mother of Joseph Schooling, said after the race, "I am sure Joseph did his best, I can tell that he is disappointed with the race, but hopefully that will spur him on for his next event."
Schooling still has another event -- the 100m fly -- to go, an event he said he was looking forward to "smash".
Swimming in the same heat, world record holder Michael Phelps also struggled, finishing third with a time of 1:55.53 seconds, but did enough to advance.
The American superstar, who is struggling to recapture his scintillating form from the 2008 Games, qualified for the semi-finals fifth fastest.
Austria's Dinko Jukic qualified fastest with a blistering time of 1:54.79 seconds.