Struggling South Korean swimmer Park Tae-hwan on Tuesday hinted at returning for his fifth Olympics, saying he owes it to himself and fans to perform better than he has at the ongoing Rio de Janeiro Summer Games.

Park missed out on the semifinals in the 100m freestyle on Tuesday at Olympic Aquatics Centre, the third time he failed to make it out of the heats in Rio. At 49.24 seconds, Park was only 32nd among 59 swimmers.

Afterward, Park said this isn't the kind of an end that he envisions, and he'd very much like to go out on top, wearing a smile on his face.

He is scheduled to compete in the 1,500m freestyle on Saturday, but Park was already looking ahead to the 2020 Tokyo Olympics, when he will be 30.

"Four years may seem like a long time, but I feel like it will come soon enough," he said. "Once I decide I want to go for Tokyo, then I will prepare for it with everything I have. Tokyo is much closer to home than Rio, and I think I can expect myself to do well there."

Earlier in the Rio Games, Park couldn't make it out of the heats in both the 400m and 200m freestyle.

Over the past two Olympics, he'd won gold and silver in the 400m free, and taken back-to-back silver in the 200m free.

After these races, Park said he didn't quite feel himself physically, but refused to blame poor showings on his relatively lack of training.

Park served a doping ban that began retroactively in September 2014 and ended in March 2016. He had to scramble to find a training facility during that period.

Park remained ineligible for Rio even after the suspension ended, because the Korean Olympic Committee instituted a rule two years ago that barred athletes from representing the country for three years after the end of their doping bans.

Park appealed the rule at the Court of Arbitration for Sport, which sided with the swimmer and made him eligible for Rio on July 8, the final day to submit the Olympic entries.

Park only entered two meets all year: the Olympic team trials in April and a minor international competition in Australia last month. He also set up a training camp in Jacksonville, Florida, and worked out there with coach Duncan Todd for two weeks before arriving in Rio.

Park said Tuesday the months leading up to Rio were "the toughest moments of my swimming career," and he tried to picture himself putting on good races to feel better about himself.

Park said Todd had some reservations about the swimmer's entering the remaining two races, because he had done so poorly in the first two.

"But I knew I could still race the 100m, and I wanted to show people I was doing my best," Park said. "It wasn't going to be easy, but I felt I had to come back here. The result wasn't very good, but I wanted to use every ounce of my energy."

Park said the 1,500m is a different story and he may well withdraw from the long distance event because he hasn't trained for it at all.

"I don't want to be seen as giving up on an Olympics that I worked so hard to make," he said. "But I don't think I should race when I am not ready. I am still giving (withdrawal) a lot of thoughts."

Park's adventures in Rio may have frustrated fans, but the swimmer said no one is as upset as he is.

"I think the two things I've said the most here are, 'It's disappointing,' and 'I'm sorry,'" Park said. "I was just upset that I couldn't do better. But in Tokyo, I'd like to contribute to the Korean delegation." (Yonhap)