Michael Phelps on his biggest loss, London plans and Ian Thorpe

The biggest loss of Michael Phelps' swimming career didn't come in an Olympics or a world championships or a U.S. national meet. It wasn't as an up-and-coming junior swimmer or Olympic hopeful. Michael Phelps say his biggest loss came three weeks ago at a little-publicized meet in Ann Arbor, six months before the year's biggest event and more than a year prior to the Summer Games in London.

Phelps touched fourth in the 200 fly at last month's Namesnik Grand Prix, snapping a nine-year winning streak in the event. In a recent interview with Fourth-Place Medal, the 14-time gold medalist said the loss hurt more than any other of his life, including his much-ballyhooed loss to rivals Pieter van den Hoogenband and Ian Thorpe in the 200 freestyle at the 2004 Olympics and his gold-snapping defeat in the same event two summers ago at the world championships in Rome.

"I really wanted that streak to continue throughout my career," Phelps said. "The Ann Arbor one is the only race I probably would want back."

The 14-time gold medalist explained that other losses in his career, and there haven't been many, were due to a lack of mental toughness or physical strength, two traits he says he's improved throughout his career. This recent loss was all on him.

"It's frustration that I've caused for myself, not training how I should be and not putting time in like I should be," he said while promoting his upcoming Xbox Kinect video game. "I think that maybe I did need to lose to be able to wake up and see what I need to improve on. It's a hard way to learn but it's probably the best way for me to learn and will stick with me longer than anything else."

After the race, Phelps said he heard comments from other swimmers that "set a little fire" underneath him. Though he wouldn't elaborate about the specific comments and who made them, Phelps revealed they were made directly to him and referenced Thorpe, who recently announced a comeback to the pool. You can fill in the blanks.

Phelps was motivated by the comments and says he relishes the idea of swimming against the man he succeeded as world's greatest swimmer.{YSP:more}

"I love it," he said of the comeback. "Being able to have a chance to race him again would be awesome. Him and I have only raced once or twice and being able to get back into the water with a competitor like him is great."

The swimming schedules of Thorpe and Phelps will be unlikely to overlap much. Historically, the 200 free is the only event the two swim together in big meets and since Phelps has confirmed that his schedule won't change much in Beijing and London, that's likely to be their only head-to-head possibility. That seems to be fine with Phelps, who's confident Thorpe's comeback will be a success.

"If he really wants to do it and is serious about it, he'll get back to the top," he said. "There's no doubt in my mind. Hopefully he wants it bad and we have a chance to go head-to-head like we have in the past."

For that to happen, Phelps says he'll need to get his training back in gear. "It needs to kick in now," he said. "There's no more time left. Worlds will be here before we know it and for me to be able to swim what I want to swim at the Olympics next year, I need to be able to prove to myself that I can swim a strong enough program this summer at that level."

His results have been middling since the 2009 world championships and in a sport like swimming, where Americans can be the third-fastest in the world in a specific event and not make the Olympic team, that won't cut it. As the 200 fly result showed, Phelps is no longer untouchable, even in his marquee event.

Phelps didn't seem worried about the prospect of getting back into peak form, though he acknowledged that being the greatest swimmer of all time isn't going to help once he gets in the pool. Reputation doesn't mean anything in a sport where the stopwatch dictates all.

Other popular stories on Yahoo! Sports:
• The most unbreakable streaks in sports
• America's most influential athletes
• Olympic hopeful rescued after being buried in sand