The decision of the International Olympic Committee (IOC) to move the Tokyo Olympic Games from this July to 2021 due to the coronavirus pandemic has raised concerns across the sporting world that some Olympic hopefuls might not be able to participate due to age restrictions, or simply because being out of form or fitness. 

Here is a list of athletes, both in China and beyond, who are most likely to be affected by the Games' rescheduling: 

Lin Dan, 36, Badminton 

The Chinese badminton superstar will be 37 by the time the Olympic Games roll around next year. 

Lin has already won gold from Beijing in 2008 and London four years later, adding to his five world titles. 

However, there is a hint of unfinished business for Lin who was defeated in the bronze medal match in Rio in 2016 having been downed in the semifinals by his rival Lee Chong Wei, the Malaysian ace he had beaten in the 2008 and 2012 Olympic finals. 

Liu Hong, 32, Athletics 

Chinese walking racer Liu Hong won the 20-kilometer event at Rio four years ago. After having a child, she made a successful comeback last year and hoped to announce her retirement with a victory at Tokyo Olympic Games. 

However, the racer admitted the Games postponement has totally disrupted her plans, including having a second child. 

"It went smooth during my training and competitions, and I was preparing to fight in Tokyo after self-isolation and adjustment," she added. "I don't want to ponder too much now. It depends."

Roger Federer, 38, Tennis 

Roger Federer, a 20-time Grand Slam winner, will be 40 in August 2021, won Olympic men's doubles gold when he partnered Stan Wawrinka at the 2008 Beijing Games.  

Federer was a quarter-finalist in singles in the Beijing Games, silver medalist in 2012 in London before injury forced him skip the 2016 Games in Rio. 

He underwent minor keen surgery last month, and remains at No. 4 at ATP world rankings. 

Serena Williams, 38, Tennis 

Serena Williams, the U.S. tennis great, will be 40 in September next year although her desire to play in Tokyo might not be as pressing as that of Federer. 

Williams already has four Olympic gold medals – singles at London in 2012 and women's doubles with sister Venus in 2000 In Sydney, 2008 in Beijing and in London four years later. 

The sisters lost their opening round match in Rio in 2016 while Serena's gold medal defence in the singles was ended by Elina Svitolina in the third round. 

Tiger Woods, 44, Golf 

Tiger Woods, who will be 46 in December next year, would have struggled to make the U.S. team for the Games if they had remained in their 2020 slot. He is currently only the sixth-ranked American with just the top four guaranteed to make the squad. 

Woods, the winner of 15 majors, has been fighting a recurrence of a back injury so at least the delay to 2021 for the Olympics gives him renewed hope of a golden swansong. 

Organizers would be desperate for Woods to play after he missed the return of golf at the 2016 Games in Rio due to injury. 

Simone Biles, 23, Gymnastics 

Though only 23, age does matter in gymnastics. A relative veteran of the field, Simone Biles cleaned up with four gold medals in Rio four years ago and topped the podium five times at World Championship last year. 

Despite a delay, Biles is still widely considered as a heavy favorite no matter when the Tokyo Olympics will take place next year. 

Andrew Bogut, 35, Basketball 

Having won an NBA title with the Golden State Warriors in 2015, Andrew Bogut has yet to claim a medal with the Australian Boomers basketball team. 

The towering center has represented Australia in three Olympic campaigns but has admitted that this season with the Sydney Kings may have been his last. 

Bogut was part of the Boomers' 2019 FIBA World Cup campaign in China, where the Aussies ranked in fourth place without claiming a medal. 

Allyson Felix, 34, Athletics 

The only female track and field athlete in history to win six Olympic gold medals, Allyson Felix had spent the last two years preparing for a golden farewell at the Tokyo Olympics. 

Felix, who turns 35 at the end of this year, will be racing against Father Time as she attempts to improve her medal tally in what will be her fifth consecutive Olympic Games appearance. 

The American star can take comfort from the fact she is by no means the oldest woman to chase Olympic glory in sprint events. Merlene Ottey was 40 when she anchored Jamaica's 4x100m relay team to a bronze medal in 2000. 

Justin Gatlin, 38, Athletics 

Justin Gatlin had planned to retire in 2020 after competing in his fourth Olympics at the age of 38. However the American sprinter now plans to extend his career in order to compete in the rescheduled Tokyo Games. 

"I think a lot of people think that time is against me or against older athletes in this situation, and it's far from the truth," said Gatlin, who has twice served suspensions for drug offences during his career. 

Meanwhile, Australia has already called for men's football at the postponed Tokyo Olympics to be changed from an under-23 tournament to under-24 so all players who helped their teams qualify can compete. 

"We would like to open up discussion with FIFA and the Asian Football Confederation (AFC) to consider adjusting the men's football tournament so that it becomes an U24 tournament for the Tokyo Olympic Games," said Football Federation of Australia CEO James Johnson. 

(With input from agencies)