Although Floyd Mayweather Jr. has retired at least twice before, boxing's pound-for-pound king says he's really taking off his crown this time.

Mayweather abruptly retired yesterday at the peak of his athletic skill and earning power, releasing a six-paragraph letter in which the unbeaten five-division champion said he no longer feels the passion that propelled him to the top of the family business.

Mayweather, a 31-year-old former Olympic bronze medalist, is calling it quits at the close of a remarkable 18-month stretch in which he beat Oscar De La Hoya and Ricky Hatton, made more than $50 million in the ring and became a bankable celebrity outside it.

"This decision was not an easy one for me to make, as boxing is all I have done since I was a child," said Mayweather, the son and nephew of three former fighters who all became top trainers. "However, these past few years have been extremely difficult for me to find the desire and joy to continue in the sport."

The WBC welterweight champ (39-0, 25 KOs) hasn't fought since knocking out Hatton last December, but was widely expected to take on De La Hoya in September in a rematch of their May 2007 bout, the richest fight in boxing history.

In the past year alone, Mayweather has appeared on "Dancing With the Stars," worked on his record label, served as the honorary starter at the Indianapolis 500 and entered the wrestling ring for a choreographed tussle with the 440-pound "Big Show" at WrestleMania in Orlando, Fla., winning what's currently his final fight with a set of brass knuckles.

TRACK & FIELD

GATLIN'S APPEAL OF DOPING CHARGES DENIED

Justin Gatlin's appeal to the Court of Arbitration for Sport on doping charges was rejected yesterday, three weeks before the United States holds its track trials.

The three-man CAS panel unanimously upheld the four-year ban given to the 26-year-old sprinter earlier this year by another arbitration panel.

Though Gatlin insists he never intentionally did anything wrong, he joined Marion Jones and Ben Johnson on the list of tainted Olympic champions. He'll also find himself in the same place as many of the competitors he tried to distance himself from — an unwilling spectator when the 2008 Games start in Beijing.

"I will continue to fight for my right to participate in the great sport of track and field in a time frame shorter than four years," Gatlin said in a statement.

But the reality is his hopes for a comeback this year are all but dead, and so are his chances of defending his 100-meter Olympic title.

Gatlin had hoped to have his ban reduced to two years, which might have made him eligible for the Olympic trials later this month.

Gatlin's 2006 positive test came as a shock to many in the track world, in large part because Gatlin held himself up as a role model for clean competition.

ELSEWHERE

Kelly Kretschman drove in four runs and Crystl Bustos hit a go-ahead two-run double to help the U.S. Olympic team overcome Cat Osterman's shaky outing in a 10-8 victory over a team of pro softball All-Stars last night at Oklahoma City. Jaime Clark homered twice off Osterman to help the National Pro Fastpitch All-Stars open a 5-1 lead, but the three-time Olympic gold medalists had enough firepower to rally for the win. ... Authorities said yesterday that a convicted steroids dealer who claimed to have sold drugs to pro football players killed himself in Dallas, and the mother of a woman found dead in his home said she believes he killed her, too. The Dallas County medical examiner ruled 35-year-old David Jacobs' shooting death Thursday a suicide, but police in the Dallas suburb of Plano aren't saying whether he shot his on-again, off-again girlfriend, Amanda Earhart-Savell, 30. ... BYU freshman heptathlete Chelsi Petersen, 20, was killed in a car crash early yesterday in Provo Canyon. According to the Utah Highway Patrol, Petersen was a passenger in a car that was making a left turn on the winding canyon road when it collided with a car coming the other way. ... Former boxing champ Thomas "Hitman" Hearns owes the federal government more than a quarter-million dollars in unpaid income taxes. The Detroit News reported yesterday on its Web site that liens filed in Oakland County state that Hearns and wife Renee owe nearly $268,000 in federal taxes from 2004-06. The seven-time world champion is a 49-year-old Detroit native and currently lives in Southfield. ... Natalie Coughlin won the 200-meter individual medley in American-record time at the Janet Evans Invitational last night at Los Angeles, a tuneup meet for the U.S. Olympic trials later this month. Coughlin touched in 2 minutes, 9.77 seconds, lowering the mark of 2:10.05 set by Katie Hoff.