Mother Superior: Serena, Azarenka Eye US Open Final

Serena Williams and Victoria Azarenka renew their rivalry Thursday when they go head-to-head in the semi-finals to determine who is mother superior at the 2020 US Open.

Williams, chasing a record-equalling 24th Grand Slam singles title, takes on unranked Azarenka, seeking a first tennis major trophy in seven years, for a spot in Saturday's final.

"Can it get any better?" Azarenka asked Wednesday after booking her place in the last four with a 6-1, 6-0 demolition of 16th-seeded Belgian Elise Mertens.

"For me, it can't. I'm so excited about this. It's an amazing opportunity to play against a champion, somebody who I respect a lot, who is my friend," added the two-time Slam winner.

Williams defeated Azarenka in the final of the US Open in 2012 and 2013.

Azarenka's last Slam title came at the 2013 Australian Open, when she retained the crown she had won a year earlier.

Her last appearance in the final of a tennis major was her US Open defeat to Williams that same year, which she lost in three sets.

Azarenka also suffered an agonising loss in 2012, when she served for the match at 5-3 in the third set only to lose 7-5.

The 31-year-old Belarusian is enjoying a fairytale run at the US Open after claiming last month's Western and Southern Open tune-up event in New York.

Both Azarenka and Williams are looking to win their first Slam since becoming mothers.

It has been more than three years since Williams won her 23rd title at the 2017 Australian Open -- when she was already pregnant with daughter Olympia.

Williams has come close since, reaching four major finals only to come away empty handed, and needs one more to match Margaret Court's record of 24.

Azarenka became a mother in December 2016. A custody battle over her son has disrupted her career in recent years but she is up to 27th in the world rankings.

Williams and Azarenka are the last remaining mothers in the draw after nine started the tournament.

Only three women -- Belgium's Kim Clijsters, Court and fellow Australian Evonne Goolagong -- have won Grand Slam singles titles in the Open era after having children.

In Thursday's other semi-final, fourth seed Naomi Osaka takes on 28th-seeded American Jennifer Brady.

Japan's Osaka, 22 is hunting her second US Open after lifting the trophy in 2018.

Brady, 25, is competing in her first Grand Slam semi-final.

Osaka, of Haitian and Japanese heritage, has been wearing different masks honoring victims of racial injustice and police brutality throughout the tournament.

She has already donned face coverings bearing the names of Breonna Taylor, Elijah McClain, Ahmaud Arbery, Trayvon Martin and George Floyd.

On Tuesday during an appearance on ESPN, Osaka was played video messages from the mother of Martin and the father of Arbery, who thanked the tennis star for her activism.

She later revealed the words of gratitude had moved her to tears.

"I often wonder if what I'm doing is resonating and reaching as many people as I hope," she wrote on Twitter.

"That being said, I tried to hold it in on set but after watching these back I cried so much. The strength and the character both of these parents have is beyond me. Love you both, thank you."