Australian Ashleigh Barty, the No. 8 seed, plays 14th-seeded American Madison Keys on Thursday in the French Open quarterfinals, after rain cancelled Wednesday's play. Sportsbooks list Barty as a -178 favorite, with Keys getting +150 as the underdog. Barty is favored by 2.5 on the "game spread," and the over-under for total games is 23. There are myriad ways to bet this match, but before you do, see what Gavin Mair has to say.

Mair is the famed women's tennis expert who called Naomi Osaka's U.S. Open championship at 32-1. Over the past two years, Mair is up an astounding 213 units on his tennis futures picks. That means if you had simply placed $100 on each of those picks, you'd be up $21,300!

Now Mair has broken down Keys vs. Barty from every angle and released an extremely strong pick.

Mair knows Keys handled Barty in the 2017 French Open (6-3, 6-2), but Barty returned the favor this February in the Fed Cup, winning 6-4, 6-1. In the most recent match, Mair noted, "Barty won 12 of the final 14 games and coaxed a whopping 31 errors from Keys' racket."

"However, Barty is very happy playing on an indoor surface but has yet to show she is a top-level player on clay," he added.

During his exhaustive analysis, Mair unearthed a critical X-factor that made him jump all over one side of this must-see quarterfinal. You absolutely need to see it before betting this match.

So who wins Keys vs. Barty? And which critical X-factor makes one side a must-back? ... Join SportsLine right now to see Gavin Mair's best bet for Keys vs. Barty, all from the acclaimed expert who's returned more than $21,000 to $100 players!