The San Francisco 49ers are double-digit underdogs for the first time in coach Jim Harbaugh's four-year tenure.

A $30,000 limit bet on Seattle was placed Tuesday and forced the MGM sports book to bump up the point spread on Sunday's game against the 49ers. The Seahawks are now 10-point favorites over their NFC West rivals.

Sports books across Las Vegas and offshore also had the Seahawks as 10-point favorites over the reeling 49ers on Tuesday. And the way the early action is shaping up, it could go even higher.

As of Tuesday, five times more bets had been placed on the Seahawks than the 49ers at the MGM. The amount of money wagered on the game was a little more even, thanks to a $20,000 bet on the 49ers that MGM assistant manager Jeff Stoneback said came from a "tourist."

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"There's already a lot of teaser and parlay money connected to the Seahawks," Stoneback said. "It's a little unusual to have this kind of (lopsided) action this early in the week, especially when you're dealing with two marquee teams. But I guess the 49ers aren't marquee anymore, when you lose to the Raiders."

The Westgate Las Vegas SuperBook opened the Seahawks as 7.5-point favorites over the 49ers on Sunday afternoon. But that was before San Francisco lost to Oakland 24-13 as an 8.5-point favorite and before Seattle pulled away from the Philadelphia Eagles. After those games played out, the SuperBook readjusted and made Seattle -9.5. The SuperBook also made the move to minus-10 Tuesday.

The loss to the Raiders was the 49ers' second in a row, dropped them to 5-8 against the spread this season and fueled further speculation of Harbaugh's future in San Francisco.

In Harbaugh's first season, San Francisco was a 9.5-point underdog at the Philadelphia Eagles on Oct. 2, 2011. Sunday's game will be the 15th time overall that the 49ers have been underdogs under Harbaugh. They are 8-5-2 against the spread in those games.

Seattle has covered the spread in the last seven meetings against San Francisco. The 49ers' odds to win the Super Bowl have plummeted all the way down to 100-1 at the SuperBook.