Apparently 22 Olympic medals aren't enough for Michael Phelps. The Olympian returns to competitive swimming this weekend for the first time since his retirement at the end of the 2012 Summer Olympics in London. The news of his comeback made a big splash last week, and it got us to thinking about other famous athletes who walked away but couldn't stay that way. Read on, Michael, for some cautionary tales—and a few gleaming glimmers of hope.
1. Michael Jordan
Jordan's 1993 retirement from the NBA was one of the most shocking departures in sports history. The greatest basketball player in history had just turned 30 and was still in the prime of his career, having led the Chicago Bulls to three consecutive NBA titles. Jordan cited boredom and the death of his father as reasons for his decision. Weirdest of all: he left to play minor league baseball. He was gone for a season and a half, flailing miserably for the Birmingham Barons double-A team before deciding he'd prefer to be spectacular at a sport he actually played well, returning to the Bulls in 1995. He led the team to another trio of consecutive championships, and then retired on top once more. But he still couldn't stay away and returned to the court in 2001 for two lackluster seasons with the Washington Wizards. He retired for good in 2003. We hope.
2. Dara Torres
Phelps is far from the first swimmer to dive back into the pool—in fact, the sport seems to breed "unretirements." He could do far worse than Torres, the dynamo whose Olympic career spanned nearly 30 years. She made her debut at the 1984 Los Angeles Olympics and went on to compete in four more Olympic Games—the most of any U.S swimmer. Her most famous comeback came for the 2008 Beijing Games, when she returned to competition at the age of 41 and won a silver medal in the 50-meter freestyle. It was the 12th medal of her career.
3. Muhammad Ali
When he returned to the boxing ring in October 1980, two years after his retirement, Ali's nickname, The G.O.A.T (Greatest of All Time), seemed more like an accurate description than a clever acronym. In his first comeback fight, the paunchy 38-year-old tried to win the heavyweight title for a record fourth time, but was pummeled by champ Larry Holmes. He lost the only other fight of his comeback, dropping a December 1981 decision to mediocre journeyman Trevor Berbick. By that time, Ali was experiencing the first signs of Parkinson's disease, which some believe was exacerbated by these two late-career beatings. He retired again, with a record of 56-5.
4. Brett Favre
The legendary quarterback turned the end of his NFL career into an annual "Will He Or Won't He?" retirement guessing game. After the 2007 season, Favre announced his retirement from the Green Bay Packers, for whom he had starred for the previous 15 years. After a change of heart, he signed with the New York Jets, where he played just one season, before retiring again—only to unretire again months later. He played two more seasons with the Minnesota Vikings—the Packers archrivals. After the 2010 NFL season, Favre threw in the towel for good.
5. George Foreman
The man behind the awesome George Foreman Grill did far more than just return to the ring in 1987 after an unprecedented full decade away—he completely transformed his image. As a young boxer, the sullen and terrifying Foreman scowled at opponents and ceded the spotlight to more charismatic rivals like Ali. After his comeback at the age of 38, he was talkative, weirdly cuddly and hugely popular. He was also shockingly effective: In 1995, at the age of 45, he won back the heavyweight title he had held 20 years prior. He also won dozens of endorsements, penned five books and starred in a short-lived sitcom. Today he spends much of his time counting the reported $150 million he earned from sales of his titular Grill.
6. Bjorn Borg
The Swede's sweet swing made him one of the most dominant tennis players of all time. Borg racked up an astonishing 11 grand slam titles over the seven-year stretch from 1974-1981. His rivalry with John McEnroe helped the sport climb to heights of mainstream popularity it has never again attained. Borg surprised the sports world when he retired in 1982 at just 26 and only a year removed from his last U.S. Open title. His time away from the game was turbulent, including divorces, personal troubles and near bankruptcy. He briefly returned to pro tennis in 1991. He failed to win a single match.
7. Lance Armstrong
When he retired from cycling for the first time in 2005, Armstrong had won the Tour de France seven straight times. He biked away from racing as the global hero who had beaten near-fatal cancer to achieve unrivaled success in his sport—despite pesky little rumors about blood doping and steroid use. He came out of retirement in 2009 to race again in the Tour de France, where he finished third. The next year, in his final Tour, he ended in 23rd place. He retired again, and two years later, he finally admitted to blood doping during his most famous wins. All of his Tour de France titles were stripped away, along with much of his dignity.
8. Mario Lemieux
Lemieux's first retirement came after the 1997 NHL season. He had won two Stanley Cups with the Pittsburgh Penguins and was one of the most prolific scorers in ice hockey history. He had also—like Armstrong—beaten cancer (in fact, Lemieux kept playing with the Penguins as he underwent chemotherapy for Hodgkin's Lymphoma during the 1993 season). After three seasons away from the ice, Lemieux returned to the Penguins, scoring a goal in his first game back. He retired again following the 2006 season.
9. Nancy Lopez
Lopez was a sensation when she first appeared on the women's golf scene in 1978. She was on the cover of Sports Illustrated and was named the Associated Press Female Athlete of the Year. When she retired in 2003, she had won 48 tournaments on the LPGA Tour. She probably could have won even more: After marrying professional baseball player Ray Knight, she played a reduced schedule over the latter part of her career to focus on raising three daughters. She returned to competitive golf in 2007, hoping to win the U.S. Women's Open, the coveted major title that had eluded her. Her comeback was brief; over two years, she failed to make the cut in any of the tournaments she entered.
10. Martina Hingis
The Slovakian-born Hingis was a grunting tennis prodigy. When she won the 1997 Australian Open at 16, she became the youngest winner of a grand slam tournament in the modern tennis era. Later that year, she reached No. 1 in the world rankings, the youngest woman ever to hold that title. From 1997 to 2002, Hingis won 9 Grand Slams and 40 tournaments. Injuries forced her to retire in 2002, but she came back four years later. She played well, rising to No. 6 in the world rankings and winning three more times. A positive drug test led to her second retirement in 2007. In recent years, Hingis—still only 33 years old—has hinted at a second comeback.