American legend Serena Williams looks focused as she chases a record-tying 24th Grand Slam title, but world No. 2 Simona Halep is waiting in the 2021 Australian Open quarterfinals at 3 a.m. ET on Tuesday. Williams' last Grand Slam title came in Melbourne in 2017, and she has been denied the milestone championship four times over the past three years. One of those near-misses came the last time these two met in the 2019 Wimbledon final. The Romanian played one of the best matches of her career, cruising to a two-set victory for her second Grand Slam title.

The latest Williams vs. Halep odds from William Hill Sportsbook list the former as the -125 favorite (risk $125 to win $100) to win the match outright. Halep is going off as a +100 underdog (risk $100 to win $100). There are a variety of other Williams vs. Halep picks you can make, including a +225 odds boost on Williams to win it in two sets and +100 on Halep to win the first set. Before you make your 2021 Australian Open women's quarterfinals picks, you need to check out the 2021 Australian Open predictions from famed tennis handicapper Gavin Mair.

Mair is the international women's tennis expert who called unseeded Jelena Ostapenko (80-1) winning the 2017 French Open, Naomi Osaka (32-1) winning the 2018 U.S. Open, Bianca Andreescu (20-1) winning the 2019 U.S. Open, among others.

Prior to the women's final in the most recent Grand Slam, the French Open, Mair picked Iga Swiatek to win (-163) in straight sets (+140) and was right on both counts. Anyone who has followed his lead is up huge.

Now, Mair has been digging deep into the latest Australian Open 2021 odds and has released his coveted best bets. He's sharing all his picks and analysis at SportsLine.

Serena Williams vs. Simona Halep preview

Mair has seen how the power Williams possesses can quickly turn Halep's strength into a weakness. The American's aggressiveness can overpower Halep's defensive approach, and she has beaten the Romanian in nine of their 11 matchups. She has won seven titles in Melbourne and showed her tenacity in a three-set victory against Belarus' big-hitting Aryna Sabalenka in the fourth round.

Halep got past Swiatek in her last match, but it was apparent early that she remains vulnerable to a big serve that can force her into errors. Williams' serve is more powerful and dependable than the 19-year-old Swiatek's, and the 39-year-old Williams is more prepared to maintain the stamina required against the speedy Halep.

The tennis expert also knows Halep's style can wear opponents down. The Romanian has the speed to cover the whole court and counterstrike against attacking players. She played a nearly perfect match the last time these two met, with a dominant 6-2, 6-2 victory at Wimbledon for her second Grand Slam title. Her style, combined with her opponent's aggressive play, could lead Williams into unforced errors.

Halep comes in with confidence after rallying to beat Iga Swiatek, who had won nine straight Grand Slam matches. Halep's 3-6, 6-1, 6-4 victory avenged her loss to the eventual French Open champion in the quarterfinals at Roland Garros and gave her 100 Grand Slam victories. After 10 unforced errors in the first set, she had just three in the second and four in the third.

How to make Williams vs. Halep picks

Is Williams' experience and consistency enough to get past the world No. 2? The tennis guru has released confident picks on the outright winner, as well as advice on how long this quarterfinal match lasts. Be sure to see Mair's picks and analysis before making your Australian Open 2021 picks for the women's quarterfinals.

Who wins Serena Williams vs. Simona Halep? And what pick could lead to a big return? Visit SportsLine now to see Gavin Mair's best bets for Williams and Halep, all from the acclaimed expert who hit it big in the last grand slam women's final.