LAS VEGAS — It wasn’t the mysterious fan with a briefcase of cash who picked this town clean during NFL gambling season.

Rather, it’s been bettors wearing a new orange Peyton Manning jersey, or Packers fans with their cheesehead hats, or Patriots fans — who loyally bet on their favored teams each week.

The problem for Las Vegas sports books is that many popular NFL teams beat the point spread during the regular season. And with many bettors combining their picks in parlays, $20 wagers turned into payouts of up to more than $1,000, depending on how many winning bets they combined.

The result is what one Las Vegas sports bookmaker called a “staggering” financial hit from the NFL regular season, as bettors handed Nevada sports books their worst year in memory.

“We know the general public now has tremendous sources of information, that the regular player is sharper than the guy 10 years ago, but we’ve never seen a streak like this before,” said Jay Kornegay, a 25-year veteran who heads the Las Vegas Hotel & Casino’s 30,000-square-foot Race and Sports book.

The damage was particularly bad in Week 9 of the NFL season, when Vegas-backed underdogs finished 2-10 against the point spread, while seven games that day finished “over” the game’s projected total-points-scored line.

Bettors adore backing the “over” and “favored” teams such as the Denver Broncos, New England Patriots, Atlanta Falcons and Green Bay Packers. As that Nov. 4 perfect storm hit, MGM Resorts, the city’s largest sports bookmaker, was forced to summon emergency stashes of cash to pay off its losses.

“It’s like you’re a passenger trapped on a train to hell,” said Jay Rood, whose 12 MGM Resorts’ sports books at properties including Mandalay Bay, Mirage and Bellagio took a seven-figure hit that day.

Kornegay dismissed the notion bookmakers can recover enough money in the NFL playoffs to make up for their losses. “We’ll just turn the page on the calendar and continue to evaluate ourselves, seeing if we need to make subtle changes,” he said.

Kornegay acknowledged he doesn’t know what those changes may be.

On Sunday evening, Kornegay and a team of bookmakers huddled by text messages to post the first point spreads for this weekend’s playoff games.

The number Kornegay most stewed over was how much to favor Green Bay by when it hosts the Minnesota Vikings on Saturday. This comes on the heels of the Packers’ loss to the same Vikings in Minnesota on Sunday. In that regular-season finale, the Packers were favored by three points.

This season, the Packers are the favorite NFL team in the Las Vegas, drawing a wealth of emotional bettors who would gamble on the team whether it was favored by 7½ or 10½ points.

The current line favors the Packers by 7½ points in Saturday’s game.

“We know people will bet the Packers regardless, but all it takes is one sharp to say, ‘Here’s $50,000 on the Vikings,’ to counteract making a [quick] line simply for the public,” Kornegay said.

Sports books also took a beating Sunday on bets made on total wins by a given team in the regular season. Kornegay said LVH took a bath on those propositions — including their line that Manning’s Broncos would win nine regular season games. The Broncos won 13.

Now, Rood is sweating out hundreds of Super Bowl winning bets made on teams such as the Seahawks, who opened at 75-1 odds.

The Indianapolis Colts were at 200-1 to win the Super Bowl after Manning left town, and remained at long odds even after Andrew Luck took over, Rood said.

Kornegay finished rattling off his point spreads for this weekend’s games and was struck by a stark reality after a season of being gutted by victorious favorites.

“Looking at this, I can tell you we’ll need the underdogs to win in every game. Again,” he said.

lance.pugmire@latimes.com

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