Las Vegas bookmakers make their money by balancing their risk, but sometimes they simply come out on the wrong side of too many bets. In fact, the results of Sunday's games were so bad for the bookies that it very well might have been their Black Sunday.

At the end of the third quarter of the early NFL games on Sunday, Las Vegas Hotels Super Book vice president Jay Kornegay knew he needed more money at the front of the sportsbook.

"I've been in this business for 26 years, and I have never seen what I saw yesterday," Kornegay said. "We call for more money a couple times a year, but never like this."

Before the day started, Kornegay and his team went over the teams that its bettors loved that week: Denver, Green Bay, Detroit, Baltimore, Houston, Chicago and Seattle.

All of them were favorites. All of them won.

The exposure for the sportsbooks doesn't occur with individual game bets; it comes in parlays, where bettors put together many bets on one card. Win them all, and it pays off big. Playing the favorites is a popular strategy.

"Think of it this way, you have people betting those teams on tons of tickets, and then you have the gambler who bet all of those teams," Kornegay said.

Kornegay said fewer bettors dared to pick from some of the games in which the favorites lost -- like Miami and Washington. And the support of Pittsburgh fans made that upset over New York less of a factor, he said.

Like Kornegay, Jimmy Vaccaro is a sports betting veteran. He has spent 37 years in the gambling world and also couldn't believe what he was seeing on Sunday

"Up until this week, the books were doing well," said Vaccaro, a spokesman for William Hill North America, which sets the lines for 150 sportsbooks in Nevada. "There were a good deal of underdogs winning outright, and we were holding an above-normal percentage. But yesterday, all the biggest favorites were winning, and we knew pretty early on it was going to be a bad day."

Without hesitation, Vaccaro called it "the worst single, regular-season, day I've ever seen."

Vaccaro said his sportsbooks did so badly because of the stakes of the game today.

"Years ago, you had about 25 percent of your business tied up in parlays," Vaccaro said. "Now, I think we're coming close to 75 percent of our business is in parlays. People are taking $60 to $70 and hoping it lands every once in a while."

Sportsbooks owned by William Hill paid out $10,400 to a gambler who bet $100 total on seven teams, $12,750 to a bettor who bet $15 that his 10 teams would win and $15,000 to a gambler who threw $5 down on a 12-team parlay.

"This is why the sport is so popular," Vaccaro said. "Because it's so uncertain who is going to win. When all the favorites win, it's a bad week. I just wish this would have happened over a three- or four-week period instead of on the same day."

At the end of Sunday, Kornegay said that he could tell that the morale of the employees in the sportsbook was not good.

"The whole team feels it," Kornegay said. "But the thing is, we could have done exactly the same thing and had a gigantic day. It's just the way the chips fall."

As if it wasn't bad enough, some sportsbooks were dealt a final blow when Atlanta, which closed at a 4½-point favorite, kicked a field goal to go up six with 17 seconds left.

"It was another kick in the ribs," Kornegay said. "But I was already on the floor."

Although it is the sportsbook's job to balance out the action, Kornegay said that no matter what, his book will come out a loser after Monday night's game between Philadelphia and New Orleans.

"We have too many bettors who need one of those teams to close out the last leg of their parlays," Kornegay said. "We're lucky the economy stinks and we're not taking the same types of bets we were four or five years ago."