Once a 50-1 long shot, Serena Williams now among favorites at US Open

Serena Williams is getting a lot of betting support as an underdog in what could be her final Grand Slam. Frey/TPN/Getty Images

An extremely popular all-time great as a betting underdog typically presents liability for sportsbooks, and Serena Williams delivered that damage with her upset in the second round of the US Open over No. 2 seed Anett Kontaveit.

Some books indicated notable losses due to a majority support of the 40-year-old American at approximately 2-to-1 odds in what many expect to be her final Grand Slam.

"It's extremely unique to have such a sports icon at long odds you would never have gotten in their prime," Caesars Sportsbook vice president of trading Craig Mucklow told ESPN, sharing the house took five times as many bets on Williams than Kontaveit. "This is a great story and the longer the run continues, the more action we'll see backing Serena, for sure."

The six-time US Open champ entered the tournament as a 50-1 long shot. Her odds lowered to 30-1 after her first-round victory and now sit at 14-1.

"The futures position is ugly," SuperBook executive director and oddsmaker John Murray told ESPN. "Liabilities can add up in a hurry at big numbers. The betting always picks up in the late rounds, and the interest around Serena will skyrocket if she keeps winning."

Given the growing legalization of sports betting across many states, it is difficult to compare betting handle to previous years. However, operators shared they are seeing much more betting interest in this tournament, given it could be Williams' final run. Caesars said it is experiencing 10 times the handle on her matches in this tournament compared to 2021.

"Certainly a much bigger handle for the early matches," DraftKings sportsbook director Johnny Avello told ESPN, also sharing they saw "fantastic" action for her second-round upset. "I would assume that trend will hold serve throughout. Liability in the futures continues to grow and will continue to multiply if she proceeds to keep winning."

To cater to the increased interest in this US Open, Caesars also offered index betting on how far she would last in the tourney. Bettors could wager in advance on the particular round she would be eliminated, which was not typically offered before.