Floyd Mayweather can make history in multiple respects when he faces Conor McGregor in their Aug. 26 super-fight. Not only does he have a chance to draw more pay-per-view buys than any other bout in history, but Mayweather could achieve the greatest professional record the sport has ever seen.

Mayweather’s career record of 49-0 ties him with the legendary Rocky Marciano, who achieved the same record as a heavyweight in the 1950s. Beating McGregor and going to 50-0 would put Mayweather in a class of his own, having gone undefeated over the course of two decades.

READ: Who Will Floyd Mayweather Fight After Conor McGregor?

Mayweather had his first professional fight nearly 21 years ago, defeating Roberto Apodaca by TKO. Following a win by unanimous decision over Reggie Sanders less than two months later, he would go on to register 12 knockouts in his next 13 fights.

The number of knockouts drastically decreased as Mayweather’s career moved on and he faced better fighters. With 26 of his 49 wins coming via the knockout, Mayweather has gone the full 12 rounds in his last seven fights. His knockout of Victor Ortiz in 2011 was controversial since Ortiz wasn’t paying attention when Mayweather sent him to the canvas, and Mayweather’s previous knockout came when he defeated Ricky Hatton in 2007.

Mayweather's last win came against Andre Berto on Sept. 12, 2015 by unanimous decision.

Without the knockout power of some other boxing greats, Mayweather has used unmatched defensive skills to avoid even one hiccup in his career. Oscar De La Hoya is the only boxer to outpoint Mayweather on a judge’s scorecard, and all but three of Mayweather’s decision victories have been unanimous.

Mayweather often isn’t put in the same category as all-time greats like Muhammad Ali, Sugar Ray Robinson and Joe Louis because he didn’t face the same level of competition. Still, he’s beaten a number of Hall of Famers, putting together a resume that’s unmatched by anyone in his era.

Defeating the likes of De La Hoya, Manny Pacquiao, Miguel Cotto, Canelo Alvarez, Zab Judah and Juan Manuel Marquez, Mayweather is unquestionably the greatest boxer in the last 20 years. He’s won titles in five different weight classes, dominating the welterweight division in the second half of his career.

Mayweather has suffered two losses inside a boxing ring, though they came before he turned pro. Augie Sanchez defeated Mayweather during the 1996 Olympic trials in a close decision, though Mayweather won the best-of-three series against his opponent. Mayweather suffered a controversial loss to Bulgarian boxer Serafim Todorov in Atlanta at the 1996 Olympics, and he was forced to accept a bronze medal in the featherweight division.

Perhaps Pacquiao could have handed Mayweather his first loss as a pro if they met when the fight was first discussed in 2009. The mega-fight didn’t take place until six years later when Pacquiao was no longer the same boxer, and Mayweather won by unanimous decision in what was considered to be a largely disappointing bout.

READ: What Is Conor McGregor's Record?

Mayweather-Pacquiao set records, drawing 4.6 million PPV buys and grossing close to $600 million in total revenue. Mayweather-McGregor could do similar numbers as the two biggest names in combat sports meet in the same ring.

McGregor, however, doesn’t even have one professional boxing match on his record, and Mayweather is almost certain to improve to 50-0.