Michael Phelps: Is the 'Baltimore Bullet' set for a return? November 15, 2013 -- Updated 1736 GMT (0136 HKT) Michael Phelps refuses to rule out a swimming comeback The American is the most decorated Olympian of all time Phelps has been tested twice by U.S. anti-doping officials since July 1 Under FINA rules, Phelps would be eligible to compete again in March 2014 (CNN) -- Is the greatest Olympian of all time making a comeback? American swimmer Michael Phelps, winner of a record 22 medals at the Games --18 of which were gold -- fueled speculation that he could stage a comeback by undergoing two drug tests over the past five months. Phelps, who seemingly brought the curtain down on his glittering career at the end of London 2012, has been tested twice by the United States Anti-Doping Agency (USADA) since July 1. By entering USADA's testing program, the 28-year-old is eligible to compete from March 2014 onwards. Swimming's global governing body FINA requires that athletes who intend to return to competition after announcing their retirement should be tested "at least nine months before he or she expects to return to competition." Michael Phelps' golfing ambitions Haney's next move Hoop dreams All-round excellence Tennis to golf Role models Baseball to golf NFL to golf Reality check Rumors of a possible return for the "Baltimore Bullet" are sure to excite swimming fans, with Phelps himself refusing to rule out a comeback. "Nothing is set in stone," Phelps told the Associated Press (AP). If I decide to keep going and swim again, then I'll compete. If I don't, I guess I'll re-retire. Just don't compare me to Brett Favre," he added, referring to the famed NFL quarterback who made a string of comebacks. Read: Phelps takes to the golf course According to the AP article, Phelps is training with his former team at the North Baltimore Aquatic Club and has shed 15 pounds. Coach Bob Bowman insisted that his return to the pool does not mean he will be lining up at the Rio Olympics in 2016. "It's premature to say that," Bowman told USA Today. What we're doing is kind of letting him have his options. He came back this fall and started to do some training with the group, mainly just to get in shape. He just felt like he was not fit. He wasn't. He's occasionally been training. He's picked it up a little more. We were just thinking about it, and I said, 'You know, you're getting in pretty good shape, maybe you want to swim in a meet?' He said, 'Well, maybe at some point.'  If Phelps was to return to action in March, his first major international meet wouldn't be the Olympics but the 2015 World Championships in the Russian city of Kazan. Phelps has claimed 33 World Championship medals dating back to 2001, including 26 golds. U.S. Sport October 25, 2013 -- Updated 1734 GMT (0134 HKT) Women dancing on the fringes of competitive sport has been labeled an echo from an age of sexism and misogyny. October 21, 2013 -- Updated 1638 GMT (0038 HKT) Former NBA player Shaquille O' Neal buys part of NBA's Sacramento Kings. CNN's Rachel Nichols has more. October 7, 2013 -- Updated 1519 GMT (2319 HKT) It was only a year and a half ago that a phenomenon swept the globe and made basketball fans a little, well, "Linsane." September 24, 2013 -- Updated 1002 GMT (1802 HKT) Soccer may be the No. 1 sport in most of Africa but basketball is growing fast and the NBA is courting the continent in a big way. June 14, 2013 -- Updated 1645 GMT (0045 HKT) Sebastien De La Cruz has become a household name after his renditions of the U.S. national anthem during the NBA Finals. May 31, 2013 -- Updated 2004 GMT (0404 HKT) OK, readers, let's have a debate: Who is the best player in the NBA? Is it Kevin Durant, LeBron James or Kobe Bryant? June 6, 2013 -- Updated 1629 GMT (0029 HKT) Tiger Woods has not only climbed back to the top of the golf rankings, he has reclaimed his crown as the world's highest-paid athlete. May 28, 2013 -- Updated 2223 GMT (0623 HKT) After a prolonged courtship with Seattle, the Sacramento Kings are officially staying put. May 27, 2013 -- Updated 2134 GMT (0534 HKT) Robbie Rogers became the first openly gay male athlete to play in a pro American sporting match when he took the field for MLS team LA Galaxy.