"If the Red Sox were a team that had won a couple of times in the last few years, this line would be more of a pick 'em," said John Avello, race and sports book director at Bally's Las Vegas. "But a lot of people want to believe this is the year."
The Red Sox haven't won a World Series since 1918, when legendary slugger Babe Ruth led the team to its fifth championship. The team's futility since Ruth's sale to the rival New York Yankees in 1920 has been blamed in baseball lore on the Curse of the Bambino.
At Bally's and Caesars Palace, the Red Sox opened as 8-5 favorites, meaning a $160 wager would win $100 if the American League champions prevail.
Initial betting moved the betting line slightly toward the National League champion Cardinals, who defeated the Houston Astros late Thursday to advance to the best-of-seven World Series beginning Saturday in Boston.
"The Red Sox opened the favorite and are still the favorite, but all the money we've received has been on the Cardinals," said Doug Castaneda, assistant manager at the Stardust Race and Sports book.
The Cardinals last appeared in the World Series in 1987 and last won in 1982.
The 3-2 line favoring the Red Sox at MGM Mirage Inc.'s eight casinos in Las Vegas became 7-5, but oddsmaker Robert Walker said wagering would continue to favor Boston "because they're very good and because of the sentimental value."
He noted that a seven-game series would include four games in Boston and three in St. Louis.
"I think the public wants to root for the Red Sox, and obviously the home-field advantage is huge," he said.