British problems continued at the World Taekwondo Championships in Mexico with Olympic bronze medallist Lutalo Muhammad losing in the last 16.
Muhammad's 10-3 defeat by Cuban Rafael Castillo in the -87kg division follows early exits by fellow GB medal prospects Martin Stamper and Bianca Walkden earlier in the week.
"My performance wasn't good enough today and I'm sorry for letting everyone down," Muhammad told BBC Sport.
The result heaps more pressure on Olympic champion Jade Jones to produce a result when she competes on Saturday.
Muhammad made a self-confessed "cagey" start to the day against Moises Molinares and trailed the Colombian 7-5 after the opening round.
However, he re-focused and powered through to a 15-11 victory and secured a tie against Castillo in the final 16.
Muhammad reined in his fast-paced attacks for his second bout against Castillo, who had looked strong in his two previous contests earlier in the day.
The Cuban edged ahead in the second round and effectively countered Muhammad's more considered moves with several successful high-scoring head-kicks which saw him progress 10-3 in the third.
"I made some tactical errors and I can't help but feel devastated right now," he said.
"There was a lot of hard work put in both ways by the coaches and the athletes so I can't blame my loss on anything but myself - it's very disappointing.
"It's not been the week I expected from me personally - I felt like I was ready to take the gold medal today."
Muhammad only made his competitive return to the sport in May having struggled with injuries after finishing third at the London Games.
However, he denied that either his preparations or the altitude - with the competition taking place 2,200m above sea-level - played a part in his early elimination.
"There's no excuses about my preparation because it was good coming here," Muhammad added.
"The only thing it [the altitude] was really going to impact was my fitness and I think my fitness was good because I was able to run at him towards the end, but that's where the mistakes were made."
Muhammad won 2012 European gold in the -87kg division but his Olympic success came at -80kg and he says he will make a decision on which category to focus on heading towards Rio 2016 when he returns to the sport later in the year.
Meanwhile, -57kg Olympic champion Jones will begin her campaign for a maiden world title after 1600 BST on Saturday afternoon and will be joined by 2011 world silver medallist Michael Harvey, who competes in the -63kg division.
With UK Sport setting GB Taekwondo a target of one to three medals at these championships, either Jones, Harvey or Damon Sansum in the -80kg class on Sunday, must claim a medal if the sport is to avoid a potential funding cut.