Floyd Mayweather has defended his decision to face Andre Berto, insisting the challenger is never involved in a dull fight.

The world's No 1 fighter believes the man he has picked to face at the MGM Grand in Las Vegas on September 12 will make sure they put on a show.

Berto (30-3-KO23) got the nod ahead of the likes of Amir Khan, Kell Brook and Keith Thurman and although he has received widespread criticism for picking him for his 49th and possibly final fight, Mayweather believes it will be worth watching.

"Every time Berto goes out there, he's in an exciting fight," he said.

"There's never a dull moment when you're watching a Berto fight, so we'll just have to see how the fight pans out."

Mayweather (48-0-KO26) will match Rocky Marciano's ring record if he beats Berto and has promised to walk away with an identical 49-0 slate.

The showdown sees Mayweather's WBC and WBA 'super' welterweight titles on the line, and goes under the name of 'High Stakes', but he is refusing to look beyond that magical mark.

"It just means I am blessed," he said.

"I took my time, stayed focused and kept my eyes on the prize and did what I had to do."