The self-appointed “Best Ever,” Floyd Mayweather has proven to be the No.1 boxer in the world, winning all 47 of his bouts as a pro. The undefeated fighter is favored to beat Manny Pacquiao on May 2 at the MGM Grand Garden Arena in Las Vegas, but the majority of the betting public is backing the underdog.

Seven weeks before the fight, Mayweather is the decided favorite at (-210), (-200) and various Las Vegas casinos. Pacquiao is a +170 underdog at both websites, and he has similar odds at other sportsbooks. But the betting line indicates that the mega-fight could be the toughest challenge of Mayweather’s career.  

"I've never seen Mayweather this low eight weeks out before the fight," Las Vegas bookmaker Jimmy Vaccaro said, via The Associated Press, a week before Mayweather and Pacquiao held a press conference to promote the fight.

"This is as close as we get to a legitimate pick 'em fight since Mayweather fought [Oscar] De La Hoya."

Mayweather was a clear favorite in his 2014 bouts against Marcos Maidana, getting -1000 and -800 betting odds. Even in his Sept. 2013 fight against Canelo Alvarez, which became the most profitable bout of all-time, Mayweather was a -300 favorite.

The betting trend indicates that the boxers’ odds will be even closer when Mayweather and Pacquiao are finally ready to meet in the ring on May 2. Mayweather announced that he would be fighting Pacquiao on Feb. 20, and he was named a -285 favorite at Before the fight was announced, some sportsbooks had Mayweather getting as high as -350 odds.

Pacquiao is a consistent favorite in his fights as well, though the odds usually aren’t as overwhelmingly in his favor. He was a -750 favorite a week before his Nov. 22 bout with Chris Algieri, whom he beat by unanimous decision amid six knockdowns. A week before beating Timothy Bradley in April for the WBO welterweight championship, Pacquiao was a -230 favorite.

Mayweather’s 2007 fight with Oscar De La Hoya holds the record for pay-per-view buys, and the unbeaten boxer was given -185 odds to come out on top. In the 2002 mega-fight between Mike Tyson and Lennox Lewis, the odds were almost identical to that of Mayweather-Pacquiao. Lewis was a -200 favorite three days before the bout, and Tyson had +170 odds.

Pacquiao has won his last three fights, though he was defeated twice in 2012. Nearly a year after his loss to Juan Manuel Marquez, PacMan defeated Brandon Rios to begin his current streak of three consecutive victories.