Tennis fans were in shock on Sunday at the news that Roger Federer forfeited his ATP World Tour Finals final match against Novak Djokovic with a back injury.
The idea of forfeiting a sporting contest is shocking, not least because it goes against the very nature of competition among peers. However, there were instances when circumstances forced athletes to forgo their competitions. Here are five occasions in which top athletes forfeited:
1. Australian Open women's singles final 2006
Walkovers are common in tennis, as sudden injuries can force players to withdraw from important matches, as Federer did. Even so, there has been only one forfeit that happened at a Grand Slam singles final, and that happened to Justin Henin-Hardenne during her Australian Open women's singles final against Amelie Mauresmo.
Mauresmo was leading 6-1, 2-0 when her Belgian opponent approached the umpire to say that stomach pain caused by anti-inflammatories meant she would have to forfeit. That meant Mauresmo winning her first Grand Slam singles title, although it could not have been more anti-climactic.
2. Qatar women's basketball team withdraws from Incheon Asian Games
Before Federer, the most recent high-profile case of match forfeiting came at the Incheon Asian Games in September, when the Qatar women's basketball team withdrew from the Games after being denied permission to wear the hijab - the Islamic head scarf - during matches. The players were asked to remove their hijabs before taking on Mongolia, but refused and forfeited.
World basketball regulations list headgear and hair accessories among the items that are prohibited on court, but after the Olympic Council of Asia issued a stern statement insisting that every athlete must have the right to participate, change may come soon.
3. England vs Pakistan, fourth cricket Test, 2006
The Test at the Oval was forfeited by Pakistan on the fourth day after a farcical stand-off following a judgment by the umpires Billy Doctrove and Darrell Hair that Pakistan had raised the quarter-seam of the ball - an illegal ball-tampering move - in the 56th over. The ball was changed and play continued, but Pakistan then remained in their dressing room in protest after tea.
The umpires then lifted the bails and awarded the Test to England. A few minutes later, Pakistan captain Inzamam-ul-Haq led his players on to the empty field but the umpires, now in their dressing room, refused to come back out. At 10pm that night, it was confirmed that England had won the Test, a result changed to a draw two years later, and back to a home victory in 2009.
4. Blackburn vs Middlesbrough, English Premier League match, 1996
The day before the Dec 21 EPL match, Middlesbrough manager Bryan Robson claimed that a combination of illness, injuries and suspensions left him unable to field a side for the game, and said he had received permission to cancel the match.
But neither Blackburn nor the Football Association were aware of the cancellation, and Middlesbrough were fined and docked three points. That three points caused the club to be relegated from the Premier League for one season.
5. Estonia v Scotland, World Cup qualifier 1996
On Oct 9, 1996, Estonia had failed to turn up for a World Cup qualifying tie against Scotland, following a dispute over the inadequate temporary floodlights that had forced the referee to change the kick-off time from the evening to 3pm.
It was assumed the match would be recorded as a 3-0 victory for the team who had turned out, the common judgment for a walkover. However Uefa subsequently decided that the match should be replayed at a neutral venue and the two sides fought out a 0-0 draw in Monaco the following February.