Boxing legend Floyd Mayweather Jr. and UFC champion Conor McGregor will step into the ring for a 12-round super welterweight boxing bout this Saturday and what promises to be an event the likes of which comes around almost as rarely as a total solar eclipse.

The matchup, which will take place at the 20,000 seat T-Mobile Arena in Las Vegas, has the potential to be one of if not the top-grossing combat sport cards in history. Estimates range from a more conservative $300 million all the way up to $1 billion, factoring in domestic and international pay-per-view (PPV) sales, merchandise, and ticket sales. For those wishing to attend in person, the cheapest tickets currently available on StubHub are going for over $1,200.

“There’s never been an event like it before and there may never be one like it again,” former HBO PPV head Mark Taffet told Variety. “When you look at these type of events, they’re more than just sporting events. They’re true entertainment spectacles. This has all the characteristics of a great spectacle where people can get together in large numbers and watch together like a Super Bowl party.”

Mayweather knows a thing or two about big spectacles, considering he has been part of multiple record-setting pay-per-views in his career. Mayweather helped set new standards in the pay-per-view buys arena with his fights against “Canelo” Álvarez in 2013 (2.2 million buys) and Oscar de la Hoya in 2007 (2.4 million buys). But both of those paled in comparison to Mayweather’s bout with Manny Pacquiao in 2015. When all was said and done, that fight did an astounding 4.6 million buys, generating approximately $400 million in domestic revenue. For his part, McGregor has been part of some of the biggest UFC pay-per-views as well, with his rematch against Nate Diaz at UFC 202 drawing 1.65 million buys in August 2016.

Fans can shell out $99 to watch Saturday’s fight on Showtime PPV in HD, or $89 for standard definition. It will also be on multiple digital platforms, with CBS and UFC making the fight available on their streaming services for the same price as PPV in a major boost for digital viewership of live sporting events.

“In the past, that audience didn’t really have an option for getting that content at home,” Stephen Espinoza, the executive vice president and general manager of Showtime Sports, told Variety. “They’d have to go to a bar or restaurant to watch it. So this will be the first time we’ve comprehensively covered that segment of the market in a calculated way. So whether it’s gaming consoles or smart TVs, telephones, tablets, mobile, web, there’s going to be multiple ways to watch it through each platform which we think will be more efficient at capturing the entire audience.”

But the question remains: Will the Mayweather-McGregor fight come close to the precedent set by Mayweather-Pacquiao?

“We would love to set a new record,” Espinoza said. “That’s a really lofty goal. And even if we fall short of it, it will still be an historic event…What we can say at this point is if we don’t set a new record we’re trending toward being easily the second-biggest pay-per-view of all time. That means that, over the last four years, Showtime and Floyd will have delivered the three biggest pay-per-views of all time in a very short window.”

Taffet, who also helped put together the Mayweather-Pacquiao fight, believes that Mayweather-McGregor has the power to be a record-breaker as well.

“When we were working on [Mayweather-Pacquiao], even if you went to the furthest right-hand column of a computer spreadsheet, we never had a number of 4.6 million buys,” he said. “The biggest pay-per-view event prior to that was Mayweather-De La Hoya in 2007. You’d have to be quite brash, if not out of your mind, to predict 4.6 million buys. So now that it has [happened], you don’t take for granted that those kind of numbers can be generated again. I do believe that this fight has the potential to set a pay-per-view record. I think not only will you see a tremendous number of buys, but you’ll see people gather in homes in larger [capacities] than has been happening in the past. Typically there have been five-six people per household watching one of these events. I think this has the potential to draw up to ten people per household for this.”

However, the Pacquiao fight was not without its detractors. After months of hype, many critics and fans took issue with Mayweather’s defensive style, while Pacquiao was later revealed to have suffered a shoulder injury prior to the fight that was not disclosed. Criticism is already being levied at Mayweather-McGregor, with most saying the fight will be incredibly one-sided given the fact that McGregor is going into the fight with no professional boxing experience.

“We’ve been wrong many times before, all of us so-called experts in sports,” Espinoza said. “I think the one thing that is attractive about combat sports is the unpredictability. The fight can end at any time and you never really know what’s going to happen until you get in that ring…You’ve got a young, strong, proud MMA champion who really has nothing to lose. If he goes out and gets beat by perhaps the greatest boxer of our generation, no one will think less of him. All the pressure is on Floyd here. If he doesn’t look good or look dominant, or even lets this guy get a little bit of success on him, it’s going to be a long night.”

McGregor is the current UFC lightweight champion and the former UFC featherweight champion. He beat José Aldo for the featherweight title in December of 2015 with a stunning knockout 13 seconds into the first round. He then defeated Eddie Alvarez via TKO for the lightweight title in November of 2016, becoming the first UFC fighter to hold championships in two weight classes simultaneously. He was forced to relinquish the featherweight belt shortly after the Alvarez fight due to inactivity in that weight class. He has a professional mixed martial arts record of 21-3, with 18 of his victories coming by way of knockout or TKO.

Mayweather comes into the fight with a flawless 49-0 record with 26 knockouts, having beaten some of the best boxers of this or any generation and captured 11 major boxing championships. He has also fought in five different weight classes during his career, fighting as a super featherweight, lightweight, super lightweight, welterweight, and super welterweight.

Mayweather is the odds-on favorite to win, given that this will be a straight boxing match rather than a MMA or mixed-rules fight. The tale of the tape is nevertheless compelling. The heaviest weightclass Mayweather has fought in during his career is super welterweight, which tops out at 154 pounds. McGregor, meanwhile, has fought as heavy as 170 pounds in two fights against Nate Diaz in the UFC, one of which he lost. Mayweather has also not had a fight in two years since he beat Andre Berto in 2015, and celebrated his 40th birthday earlier this year, while McGregor recently turned 29.

“I’ve said to some people it reminds me a little of an Evel Knievel jump, where you want to see if Evel can make it across the canyon or not,” Taffet said. “But the truth is [McGregor] may make it, and if he does, it will be one of the greatest sporting achievements of all time…I think McGregor will make the kind of effort that will make his fans proud and reward them for watching the event, and as a result there’s a chance that everyone could walk away a winner regardless of the outcome of the fight.”