The favourite is struggling for form and fitness, while the defending champion is out of sorts, so the Wimbledon women's draw could produce upsets, says Max Liu.
"Barty 8.27/1 and Osaka 9.617/2 are among the leading contenders in the betting. However, neither player has been beyond the third round so far."
With little over a fortnight to go until Wimbledon 2019 begins the women's draw looks wide open with favourite Serena Williams trading as long as 6.86/1 in the winner market.
While the men's draw sees Novak Djokovic heavily backed into 2.6813/8, bettors think the women's contest is much more difficult to gauge.
That's hardly surprising when you consider that so far this year the Grand Slam's have produced upsets in the women's draw, with Ashleigh Barty and Naomi Osaka victorian in France and Australia respectively.
Barty 8.27/1 and Osaka 9.617/2 are among the leading contenders in the betting. However, neither player has been beyond the third round so far. Mind you, at 23 and 21-years-old respectively both have plenty of time to improve on that.
Williams has won Wimbledon seven times but she was knocked out of this year's Australian Open in the quarter-finals and the third round at Roland Garros. And yet she's the favourite, in part due to her peerless record at SW19 and bettors' uncertainty about the new pretenders to her crown.
Defending champion Angelique Kerber is 18.5, as she has failed to reach the last eight in either of this year's slams, while Petra Kvitova, who has won this tournament twice, is 12.011/1 and Karolina Pliskova is trading at 16.5.
Britain's Johanna Konta 20.019/1, fresh reaching the last four in Paris, will be desperate to improve on last year's second round exit.