Olympic gold medallist Daniel Wiffen feels “something’s going wrong” with his performances at the World Aquatics Championships in Singapore.

On Tuesday, the swimmer from Magheralin in Northern Ireland only scraped into the 800m freestyle final after finishing fifth in his heat with a time of seven minutes, 46.36 seconds.

The 24-year-old, who suffered from a bout of appendicitis during the build up to the competition, is the defending champion in the event but he will be in an outside lane for Wednesday’s final.

Wiffen said he will still be going into the race with the mindset that he can retain his title despite the less than ideal preparation.

“Obviously pretty disappointed with the overall swim of the 800, but we’ve got a lane so we’ve got a chance to defend my title and I’m going in with that mindset that I can win this still, even though I’m eighth in,” said Wiffen, who failed to make the final of the 400m freestyle.

“I just feel really weak at the moment. I felt it in the 400 and then I felt it in the 800 free, so something’s going wrong.

“I just need to figure out what it is and then change it for [Wednesday] night’s final.”