In an unsatisfying conclusion to a much-anticipated bout, Floyd Mayweather Jr. defeated Victor Ortiz in a fourth-round knockout in Las Vegas on Saturday night to capture the WBC welterweight championship belt.

After an unprovoked lunging head butt by Ortiz, Mayweather responded by delivering a quick-start combination to Ortiz immediately after Ortiz put his fists to Mayweather's in an act of goodwill and apology.

The left and right combo by Mayweather were intended to knockout Ortiz, and it did just that. Ortiz failed to stand after veteran referee Joe Cortez's 10 count.

It didn't seem as though Cortez had done an adequate separation of Mayweather and Ortiz, but that didn't stop Mayweather from retaliating after the headbutt.

I took the break by the referee and I obeyed exactly as I was told, Ortiz said, according to ESPN. And then, boom, he blindsided me. 

The headbutt was so blatant by Ortiz that some might say that Mayweather's reaction was justified. It could have done serious damage to Mayweather, and it seemed that the undefeated fighter regarded the action by Ortiz as an underhanded move that deserved a harsh retaliation.

He did something dirty when it was his corner who said I was dirty, Mayweather said. But I won the fight. 

Mayweather appeared to be winning the round, and probably deserved to be leading three-rounds-to-one in the fight. Ortiz had been boxing with solid results as an underdog who had a decent chance of pulling off an upset.

Mayweather remains undefeated with a record of 42-0, and living up to the prediction that he would win by scoring the knockout. Ortiz's record drops to 29-3-2. 

The Mayweather victory might pave the way for a megabout with Manny Pacquiao. The Filipino boxing legend faces Juan Manuel Marquez, in November.

A Pacquiao-Mayweather bout might garner both fighters a $50 million payday.