Brent Musburger describes how the head bookmaker at a Las Vegas casino will handle an excessive wager after "Bettor X," who won a huge World Series payday, placed a bet on Philadelphia to win the Super Bowl. (1:28)

The same unnamed bettor who took Las Vegas for millions on the World Series is back looking for another big score on the Super Bowl.

He's betting on the underdog Philadelphia Eagles for big bucks.

William Hill U.S. on Monday became the second sportsbook to report taking a $1 million bet on the Eagles. Director of trading Nick Bogdanovich said his book accepted a $1 million money-line bet on Philadelphia at +165 odds.

The bet, which was first reported by Covers.com, would net $1.65 million if the Eagles pull the upset.

Last week, MGM reported taking a "multimillion" dollar bet on the Eagles, and sportsbook operator CG Technology and the South Point each have taken money-line wagers on the Eagles for $700,000 and $500,000, respectively.

Johnny Avello, executive director for Wynn Race & Sports, told ESPN that he also took a "good-size, six-figure" money-line bet on the Eagles, adding to what had already been lopsided action on Philadelphia.

Multiple sources told ESPN that they're all from the same bettor who went on a winning streak during the World Series that contributed to Nevada's books losing $11.4 million on baseball in November, the books' worst baseball month ever.

The customer's name has not been revealed. Some referred to him as "Bettor X" in October, when he placed a series of the largest money-line bets on the World Series, winning each one.

"He's one of the guys who was floating around betting all that money on the World Series," veteran Las Vegas bookmaker Jimmy Vaccaro, now of the South Point, told the Associated Press. "I don't think he lost a bet then, we'll see how he does now."

"Yeah, I've got him, too," Avello said Monday of the return of the World Series bettor.

The New England Patriots were 4.5-point favorites over the Eagles on Monday at the majority of Las Vegas sportsbooks. The money line was down to New England -180, with Philadelphia paying back +180.

"There's been some good-sized five-figure bets coming in [on the Patriots]," Avello said. "There are people playing the Patriots, but it's just that the Eagles were just so heavily bet early, seemed like everything was going that way."

Nearly 80 percent of the money bet on the point spread was on the Eagles at the Westgate Las Vegas SuperBook, including some wagers placed by respected bettors Monday. The Westgate SuperBook trimmed the point spread to Patriots -4 after "some people we respect bet Eagles +4.5," assistant manager Jeff Sherman told ESPN. That bet was not from Bettor X, a source said.

A record $138.4 million was bet on last year's Super Bowl at Nevada's sportsbooks. Many books are projecting this year's handle to easily surpass last year's amount.