Bjorn Borg retired after winning five straight Wimbledon titles. Photo / Getty
The sudden retirement of Italian tennis player Flavia Pennetta was a surprise to everyone this morning, with the US Open champion announcing her retirement at the top of the tennis world.
The 33-year old Pennetta beat Roberta Vinci in this morning's US Open final, before calling it quits in the on-court post-match interview.
The Herald chronicles some of sport's other surprising retirements.
Michael Jordan
Jordan stunned the sporting world in 1993, announcing his retirement from basketball just before his dominant Chicago Bulls side were set to defend their three consecutive championships.
His reasoning? He wanted to try crack Major League Baseball, something which did not go well, leaving him to return to the NBA, where he won another three titles and two more MVP's.
Jordan threw in two more retirements for good measure, but none will match the shock provided by his 1993 announcement.
Ryan Harris
The Australian fast bowler retired just before this year's Ashes series due to a knee injury. His age (35) wasn't the surprising part, with Harris having played in the warm-up matches before the Ashes began, before calling it quits just before the big series got underway.
Bjorn Borg
Borg left tennis at his peak, retiring at the age of 26 after having won five straight Wimbledon titles and 11 Grand Slams.
The Swede was on track to break nearly every record in the book - and had broken many of them already - but he decided to walk away due to a lack of enjoyment of the sport.
Nearly 10 years later, Borg tried to return, but found his wooden racket was hopelessly out of date, and his skills declined, failing to win a single match in his return to the sport.
Chris Borland
In a retirement which is the most thought-provoking of recent times, Borland walked away from the NFL after an impressive rookie season, citing a concern about the health dangers of the sport, most noticeably concussions.
Borland was looked at as a future key for his San Francisco 49ers side, but he explained his retirement by saying "from what I've researched and what I've experienced, I don't think it's worth the risk."
Many other 49ers followed his suit, including offensive lineman Anthony Davis and linebacker Patrick Willis.
Joseph Sullivan
From a gold medalist rower at age 25, to a firefighter at age 27, Joseph Sullivan's career has certainly taken on an interesting trajectory.
Sullivan was one of the young stars of New Zealand rowing, winning back-to-back gold medals at the World Championships in the double sculls alongside Nathan Cohen, before winning the gold at the London Olympics with the memorable late charge that was voted New Zealand's favourite sporting moment at the Halberg Awards.
Sullivan was made a member of the New Zealand Order Of Merit in 2013, but since that time he failed to regain his lofty heights of prior years, eventually retiring last year to work for the Fire Service.
Tim Brown
Tim Brown was a constant selection for both the Wellington Phoenix and the All Whites, but he decided to take a different path at age 31 in a move which surprised many.
Brown could have kept up his role in the middle of the park for New Zealand's premier footballing sides, but instead he took up a chance to complete a masters degree in management in England.
Justine Henin shocked the tennis community when she announced her retirement in 2008
Justine Henin
Henin was on the top of the female tennis world when she retired in 2008 - being ranked world No. 1 and considered the favourite for the upcoming French Open, where she was set to be the three-time defending champion.
The year before, Henin had only lost four matches (winning 63), and had been ranked as the world's best for over a year. Additionally, she was still in the peak of her prime at age 26.
Much like other early retirees, Henin returned, and although she had more success than Borg - making the 2010 Australian Open final - she didn't have the pure dominance of her earlier years and eventually pulled the pin for good in 2011.
Mark Spitz
A legend of swimming, Spitz retired at the remarkably young age of 22, and on arguably the highest note any athlete has ever retired on.
After winning four medals at the 1968 Olympics in Mexico City, Spitz won an unprecedented seven gold medals in 1972 in Munich, setting a world record that stood until 2008, when Michael Phelps claimed eight in Beijing. Spitz also set world records in every event he raced in at the 1972 Olympics, a record that is unmatched to this day.
The only thing more stunning than Spitz's accomplishments was his decision to immediately retire.
Spitz initially planned to become a dentist before largely living off his lucrative endorsement deals. Unlike many others who gave up sport young, Spitz never did return to the pool.
Bernice Mene
Mene was one of the standout Silver Ferns of her era, debuting at 17 and being a force to be reckoned with for a decade at the goal defence position.
After 10 years in the side, Mene retired at age 27, with the surprise announcement being even more unexpected due to her being the long-term captain of the national team. With many netballers playing into their mid-to-late 30's, Mene's decision was an outlier at the time.
Mene played 78 tests for the Silver Ferns, and explained her decision as a want to explore other career options outside of netball.
The cyclist was never referred for a detailed psychological assessment.