Shane Mosley (R) is 1-3-1 in his last five fights, but has no plans to retire (AP)One of the saddest sights in professional sports is trying to watch a one-time great who is well past his or her prime still trying to compete.

Willie Mays played long past his prime (AP file photo)Willie Mays is, arguably, the greatest all-around player in Major League Baseball history, but if you only saw him playing for the New York Mets in the 1973 World Series, you'd have a hard time believing that.

Similarly, Johnny Unitas is one of the best quarterbacks to have ever lived, but definitely not to those who only saw him play for the San Diego Chargers.

There have been countless boxers in similar situations and fans and media routinely plead with them to retire. Most recently, Roy Jones Jr. and Evander Holyfield have fallen in that situation, fighting on long since their skills have left them.

Shane Mosley, the one-time lightweight, welterweight and super welterweight champion who is one of the best fighters of the last 20 years or so, is another of them.

Shane Mosley's Twitter accountMosley defeated Pablo Cesar Cano by a unanimous decision on Saturday in Mexico,

A recap of the highest-profile boxing matches of the weekend.

Lucas Matthysse has huge power in both hands, although it was the left hook that took down Lamont Peterson. (Getty Images)

A Star Emerges

Lamont Peterson entered Saturday night's bout with Lucas Matthysse regarded by many as the finest 140-pounder in the world.

He left in a heap.

What was expected to be a highly competitive bout turned into a showcase for Matthysse. The Argentinean might just be the best pound-for-pound puncher in the world and emerged as an intriguing opponent for Floyd Mayweather Jr. with the performance.

Matthysse (34-2, 32 KOs) knocked down Peterson twice in the third round with a pair of left hooks before referee Steve Smoger stopped the fight at the 2:14 mark.

Peterson, who came in one pound above the junior welterweight limit, had the right idea in the first round by boxing, using his feet and staying away from Matthysse. Peterson (31-2-1, 16 KOs) then elected to be a bit more stationary and jab in the second round before being knocked down with a looping left hook that completely changed the fight.

The problem for Matthysse?

(Warning: Video contains strong language so viewer discretion is advised.)

LAS VEGAS -- It was hardly the classiest tactic, but trainer Ruben Guerrero injected plenty of intrigue into his son Robert's upcoming welterweight title bout with Floyd Mayweather Jr. on Wednesday.

After a boring thank-you fest disguised as a news conference in the MGM Grand's Hollywood Theatre, promoter Oscar De La Hoya invited Ruben Guerrero to the dais to say a few words. Virtually every other speaker had gone on in a monotone fashion, thanking every entity possible, name-dropping sponsors ad nauseum and predicting a great fight.

Ruben Guerrero (R) calls Floyd Mayweather Jr. "a woman beater" as Robert Guerrero looks on (AP)Ruben Guerrero, who has been trying to steal the spotlight from his son by, among other things, challenging Mayweather's father to a fight, changed things quickly.

He ranted and raved like a madman, shouting about Mayweather's domestic violence conviction that forced the pound-for-pound top boxer to spend 57 days in a local jail last year.

He started slowly, alluding to his challenge to