Las Vegas sports books are sweating the Kansas City Royals and Houston Astros heading into the final 2½ months of the season.

The Royals are the consensus World Series favorites in Vegas. They are listed at 4-1 at the MGM sportsbook and have been attracting some significant wagers since early in the season.

Odds to win '16 World Series Royals 4-1 Cardinals 9-2 Nationals 5-1 Dodgers 6-1 Astros 8-1 Pirates 12-1 Angels 12-1 Yankees 15-1 Giants 15-1 Cubs 15-1 Blue Jays 18-1 Tigers 20-1 Orioles 20-1 Mets 20-1 Rays 22-1 Indians 25-1 Rangers 30-1 Twins 30-1 Red Sox 50-1 Mariners 50-1 Padres 50-1 Athletics 60-1 White Sox 75-1 Diamondbacks 100-1 Braves 150-1 Marlins 200-1 Reds 250-1 Rockies 250-1 Brewers 500-1 Phillies 1,000-1 -- Courtesy of MGM race and sports

"We took some pretty heavy action on the Royals the first weekend of the season," MGM vice president of race and sports Jay Rood said. "A gentleman bet them three times, at 18-1, 15-1 and 10-1, all the way down, between $25,000 and $30,000 a pop."

William Hill's Nevada sportsbook took a $7,500 futures bet on the Royals at 28-1 on April 12.

The St. Louis Cardinals are the second favorites at 9-2, followed by the Washington Nationals (5-1) and Los Angeles Dodgers (6-1). The Astros, after opening at 100-1, are down to 8-1 at MGM.

"We're on the hook for a seven-figure risk at 100-1 [on the Astros]," Rood said.

While the Royals are No. 1 in money wagered at William Hill and the Westgate SuperBook, the Chicago Cubs still own the distinction at the MGM. Nearly 4,000 bets have already been placed on the Cubs to win the World Series at MGM properties. That's more than double the number of bets on any other team. Chicago is currently listed at 15-1. The Cubs (47-40) are in third place in the National League Central, 8.5 games behind the Cardinals.

At the MGM, the New York Yankees are 15-1, along with the defending World Series champion San Francisco Giants. The Boston Red Sox are 50-1.

The Texas Rangers are a popular pick at the Westgate, where only the Royals have attracted more money. William Hill took a $4,000 bet on the Rangers at 75-1 on June 18.

The Cincinnati Reds have seen their odds decrease the most. The Reds opened at 18-1 and are now 250-1 at the MGM.

The Philadelphia Phillies are the biggest long shots on the board. They are 9,999-1 to win the World Series at the Westgate. Some people still believe, though. On June 18, a bettor put $500 on the Phillies to win the World Series at 1,000-1 at William Hill. Philadelphia (29-62) is 21 games back of the Nationals in the NL East.