The 28-year-old has been the number two to Manchester City's Joe Hart since last year's World Cup but has had a series of injury problems and has made the decision to benefit his club career.
It is far from the most shocking retirement in sporting history, but has inspired us to look back at some of those retirements that rocked the world.
We have decided to stick with a one entry per sport rule, so let us know what you think at the bottom of the article, as well as any you feel we might have missed.
Michael Jordan - Basketball
Basketball might not be the most popular sport in the UK, but even in these parts Jordan was a sporting megastar when he retired in 1993 (on the first of three occasions). After leading the Chicago Bulls to three straight NBA titles and a host of personal awards he decided to quit the sport and take up baseball. Jordan made the decision in honour of his father who died earlier that year, but he was back in time for the 1995-96 season and again led his side to three more titles in a row.
Lorena Ochoa - Golf
Ochoa stunned the world of golf when she announced she was quitting the sport last year at the age of just 28. The Mexican had dominated the women's tour for the previous three years with a string of titles, including two Majors, which made her the biggest sports star in football-mad Mexico, where golf had previously been seen as a pastime for a tiny wealthy elite. Ochoa said at her retirement press conference: "I realised I didn't feel that motivation and that I wanted to start a new life." However she has still kept her LPGA card so she can play in her own Lorena Ochoa Invitational and has said: "I'm going to leave the door open in case I want to come back in one or two years to play a US Open or a Kraft Nabisco."
Rocky Marciano - Boxing
Rocky Marciano remains the only heavyweight champion to retire undefeated. He called it quits in 1956 a few months after knocking out skilful veteran Archie Moore. Perhaps the most surprising thing is not that Marciano retired at the relatively young age of 32, but rather that he managed to resist the temptation to ever come back like so many other boxers. He did consider a comeback in 1959 when Ingemar Johansson won the heavyweight championship from Floyd Patterson but he abandoned those plans after just a month back in the gym. He finished his career with 49 wins from 49 fights (43 of which came by way of knockout). He died in a plane crash in 1969 the day before his 46th birthday.
Bjorn Borg - Tennis
In 1981 Bjorn Borg was still the top tennis player in the world. He had won 11 Grand Slam titles, compiled the record for most consecutive wins in tennis history (43) and was a superstar around the globe. However, after losing to great rival John McEnroe in the 1981 US Open, the spark left his game and he would only win two matches in limited action in 1982 before announcing his retirement in 1983. McEnroe asked him to change his mind but Borg was resolute. The news shocked everyone in tennis. Arthur Ashe told Sports Illustrated: "I think he could have won the Grand Slam. But by the time he left, the historical challenge didn't mean anything. He was bigger than the game. He was like Elvis or Liz Taylor or somebody. He'd lost touch with the real world." Borg would make the odd fleeting comeback but never became a big player on the ATP Tour again.
Johan Cruyff - International football
Johan Cruyff was the star of the Dutch team that reached the 1974 World Cup final and then helped the team qualify again for the 1978 edition in Argentina, although he would never play in that tournament. Cruyff retired from international football in October 1977 with the original reason being that he was against the military dictatorship that was in power in Argentina at that time. However, in 2008 Cryuff said it was because he and his family were involved in a kidnap attempt in Barcelona a year before the tournament and he didn't want the strain of being away from them. "To play a World Cup you have to be 200 per cent okay," he told Spanish radio. "There are moments when there are other values in life." Despite being one of the greatest international players of all-time Cryuff only played 48 times for the Netherlands, scoring 33 goals. The Dutch again reached the final without him but lost to hosts Argentina in the final.
Florence Griffith-Joyner - Athletics
'Flo-Jo' was the golden girl of the 1988 Olympics in Seoul as she won gold in the 100m, 200m and 4x100m. The American sprint queen ran an astonishing 10.49 in the US Olympic 100m trials to get to South Korea and 21.34 in the 200m final in Seoul - world records that remain to this day. However, she was dogged by rumours of drug abuse throughout her career, despite never failing a test, and then retired after the Olympics. Ten years later she died in her sleep after suffocation during a severe epileptic seizure. Her husband requested that Joyner's body specifically be tested for steroids after her death in a bid to clear her name but was informed that there was not enough urine in her bladder and that the test could not accurately be performed on other biological samples.
Bobby Fischer - Chess
US chess prodigy Bobby Fischer became world champion in 1972 after beating Boris Spassky in the most famous chess encounter of all-time, but then refused to play another competitive game for nearly 20 years. Erratic and demanding at the best of times, Fischer was due to face Anatoly Karpov in 1975 to defend his title but withdrew after the chess authorities refused to agree to all his demands. Fischer's comeback match was again against Spassky in Yugoslavia in 1992 in spite of a United Nations embargo banning sporting events in the country. Fischer called a press conference where he spat on a US order forbidding him to play - meaning he was forced to spend the rest of his days in exile. He went on to make a number of anti-American, anti-Israeli and anti-Semitic statements over the latter years of his life and even wrote a personal letter of support to Osama Bin Laden soon after September 11. He died from degenerative renal failure in 2008 while living in Iceland.
Juan Manuel Fangio - Formula One
The Argentine speedster retired in 1958 after having won the world championship for the past four seasons. In total he won five world titles with four different teams and his record was not broken until a certain Michael Schumacher came along more than 40 years later. Fangio could have achieved even more if he wanted to but decided to call it quits because he simply had nothing left to prove. As David Tremayne wrote in Fangio's obituary for the Independent: "He retired at Reims, midway through 1958, at the age of 47, holding strongly to his own belief that champions, actors and dictators should always quit at the top."
Shaun Tait - Cricket
Lightning-quick paceman Shaun Tait announced his retirement from cricket's one-day format in March this year to focus his energies on the lucrative Twenty20. Tait may only be 28 years old, but a violent and unstable action has led to persistent back problems over the years and, throwing in a hefty dose of homesickness on tour, the paceman had simply had enough, losing his passion for the game. No Tests, no ODIs, no serious international cricket; Tait will now have to content himself with run-outs in the IPL, the Champions League and the Big Bash. It's cricket's loss.
Pat Tillman - NFL
American football star Pat Tillman was enjoying a lucrative career playing for the Arizona Cardinals in the NFL when he decided to turn down a $3.6 million contract to enlist in the American army eight months after the September 11 attacks. Tillman served several tours in combat in Iraq and Afghanistan but was then tragically killed in Afghan mountains in 2004. The Army tried to claim that he had been killed by enemy fire but a cover-up was later unearthed that revealed that he was actually killed by 'friendly fire' when one Allied group fired upon another in confusion after nearby gunfire was mistakenly believed to be from enemy combatants. His case was to be the subject of a series of controversial congressional inquiries.