What if McGregor won? Four times Vegas sportsbooks lost big

This was an unwelcome sight for Las Vegas bookmakers. David Rosenblum/Icon Sportswire

Some old-school bookmakers, guys who have seen sports betting in Las Vegas evolve over the past 40 years, weren't super fired up when the Floyd Mayweather-Conor McGregor fight was made official in June.

With Mayweather such a heavy favorite, they weren't convinced that the fight would generate that much betting interest. But it will go down as the most-bet fight in Nevada history.

"One of the biggest boxing wins [for our sportsbook]," MGM vice president Jay Rood told ESPN in a text message after the fight.

A lot has changed over the past four decades. In 1987, bets totaled $1.3 billion at Nevada sportsbooks. This year, the books are on pace to handle more than $5 billion. So naturally, since more money is being bet, the biggest decisions the books face are also growing to unprecedented amounts.

Mayweather-McGregor is the perfect example.

"On a boxing match, I think it will be [the biggest decision we've had at our books]," said Ed Malinowski, sportsbook director at the Stratosphere hotel and casino in Las Vegas.

Bookmakers came out ahead when Floyd Mayweather won on Saturday night, but here's a look back at several of the other big decisions Las Vegas sportsbooks have faced recently:

Mike Tyson vs. Evander Holyfield

Date: Nov. 19, 1996

It was the beginning of the end of Tyson's domination of the heavyweight division, and bookmakers weren't ready for it. Tyson opened as a -2500 favorite over Holyfield at MGM's sportsbook. Richie Baccellieri was running the book at Caesars Palace and decided to make the price a little shorter. The first big bet they took on Tyson was $68,000 at -1700 to win $4,000.

"That might have been the last bet we wrote on the favorite in a month," Baccellieri recalled.

The price on Tyson shrunk dramatically leading up to the fight, down to -500 or less at some books. Baccellieri said they pulled out all the stops trying to get action on Tyson from professional players. It wasn't enough to even out all of the money on Holyfield, who dominated for the majority of the fight and stopped Tyson in the 11th round. Caesars Palace took a bath.

"We did everything we could and still went into the fight three-quarters of a million long on the 'dog," Baccellieri said. "We used to have an inventory of race and sports chips at Caesars that was always very low, because all the big players, the sharp guys had them. We got them all back that night."

National championship game, Clemson Tigers vs. Alabama Crimson Tide

Date: Jan. 9, 2017

Clemson's last-second touchdown to beat Alabama in last season's title-game thriller delivered multiple Nevada sportsbooks their worst loss ever on a college football game. William Hill reported that Clemson's 35-31 win cost the book a "seven-figure" loss.

"It was as bad a result as humanly possible," William Hill director of trading Nick Bogdanovich, a veteran Las Vegas bookmaker, told ESPN the day after the game.

Holly Holm vs. Ronda Rousey

Date: Nov. 14, 2015

The Stratosphere sportsbook had enjoyed a very profitable college football Saturday, but it was all gone when Holm knocked out the heavily-favored Rousey in the second round.

"We had a great, great college football Saturday," said Malinowski, "and then Holm wiped all [of] it away."

Holm closed as high as an 8-1 underdog and attracted the bulk of the bets. For every one bet on Rousey at MGM's sportsbook, there were 50 on Holm. Holm's upset of Rousey delivered the largest loss for a UFC fight ever for MGM.

1991 World Series, Minnesota Twins vs. Atlanta Braves

The Twins and Braves, a pair of last-place teams the previous season, had sportsbooks in a million dollars by the time they reached the 1991 World Series.

The Twins finished 14 games under .500 the season before, and the Braves had lost 97 games. They were the dregs of baseball with World Series odds reflective of that. To start the season, the Twins and Braves had odds as high as 200-1 and 300-1 at some books.

"We were in a no-win situation with either of those teams," Bill Sattler, director of specialty games for Caesars Entertainment, recalled. Although there was little difference, the Twins beat the Braves in a thrilling seven-game World Series.

In November, the month after the World Series, when patrons would have been cashing in their futures bets, Nevada sportsbooks lost $950,000 on baseball, according to state gaming control.

Super Bowl XLVIII, Denver Broncos vs. Seattle Seahawks

Date: Feb. 2, 2014

To be fair, Las Vegas has won its fair share of big decisions as well, including in Super Bowl XLVIII between the favored Denver Broncos and the Seattle Seahawks.

The books won a record $19.7 million on the Seahawks' 43-8 blowout of Peyton Manning and the Broncos. It smashed the previous most lucrative Super Bowl for the books by more than $4 million.

Since the Nevada Gaming Control Board began tracking wagering on the Super Bowl in 1991, the state's regulated sportsbooks have come out ahead in 25 of 27 games. The books are up a net $173.6 million on the Super Bowl during that span.