Casinos have a lot at stake as the Tom Brady free-agency frenzy draws near.

After 20 seasons in New England, the Patriots remain the favorite to land the six-time Super Bowl champion, but recent trends suggest that a Brady-49ers marriage will cost Vegas the most money.

“I can tell you this. We don’t want to see [Brady] sign with the 49ers,” South Point casino sportsbook director Chris Andrews told USA Today. “We’d lose pretty good.”

The market shift is a response to a report from Patriots insider Tom Curran, who floated the idea of Brady and Jimmy Garoppolo switching places last week.

Another sportsbook at the Westgate Las Vegas has seen a spike in money wagered on the 49ers as well. After opening at 100-1 odds, the team has rapidly moved to the third choice at 8-1 and have the second-most money wagered behind the Tennessee Titans.

“The 49ers are beginning to get some interest with the latest rumors,” Westgate’s vice president of race and sports operations Jay Kornegay said.

“The flavor of the day is the 49ers,” said Westgate’s vice president of risk, Jeff Sherman. “At the end of last week, the media was talking about the Niners as a possibility, then people started betting them.”

Amid the seemingly never-ending cacophony of rumors, Brady’s future is still very much up in the air. The bets remain “spread out everywhere,” according to Sherman, and as perhaps the most crucial free-agent domino, the 42-year-old is driving a lot of the handle in the betting market as a whole.

“We have had guests come in and take shots on some NFL Division futures based on where they think [Brady] will land,” Borgata’s director of race and sports Tom Gable told the Post. “Someone placed a five-figure wager on Tampa Bay to win the division (NFC South) solely based on the customer’s inclination that Brady is going to sign with Tampa Bay.”

NFL free agency will begin on March 18.