Australian Open 2021: Serena Williams, Novak Djokovic Headline Tuesday Results

Serena Williams and Novak Djokovic were among the players to punch their ticket to the 2021 Australian Open semifinals during Tuesday's play at Melbourne Park.

Williams is now two wins away from tying Margaret Court for the most Grand Slam singles titles in history at 24 after beating Simona Halep. She'll face off with three-time major champion Naomi Osaka, who cruised past Su-Wei Hsieh in the day's other women's quarterfinal.

Djokovic already holds the men's Australian Open record with eight championships and he's once again the player to beat after a hard-fought win over Alexander Zverev. Next up is a clash with Russian qualifier Aslan Karatsev, who upset Grigor Dimitrov in the quarters.

Tuesday's Australian Open Results

Men's Draw

(1) Novak Djokovic d. (6) Alexander Zverev; 6-7 (6), 6-2, 6-4, 7-6 (6)

Aslan Karatsev d. (18) Grigor Dimitrov; 2-6, 6-4, 6-1, 6-2

Women's Draw

(10) Serena Williams d. (2) Simona Halep; 6-3, 6-3

(3) Naomi Osaka d. Su-Wei Hsieh; 6-2, 6-2

Williams successfully executed a high-risk, high-reward style of a play against the defensively strong Halep. She recorded 24 winners, including five return winners, and four aces while winning 49 percent of the points on the second-seeded Romanian's serve, which helped offset her 33 unforced errors.

It was an impressive performance after she was pushed to a third set by No. 7 seed Aryna Sabalenka in the previous round and bodes well heading toward the semifinals.

"I definitely think this is the best match I've played this tournament for sure," Williams told reporters. "Obviously I had to, going up against the No. 2 in the world. I knew I had to do better and that's what I did."

Hsieh scored upsets over No. 8 Bianca Andreescu and No. 19 Marketa Vondrousova en route to the quarterfinals, but she was no match for Osaka on Tuesday.

The 23-year-old Japanese superstar was highly efficient, tallying 24 winners and seven aces with just 14 unforced errors. She also won 23 of the 25 points played on her first serve (92 percent).

Osaka holds a slight 2-1 edge in previous official WTA Tour meetings with Williams, but they haven't faced off since 2019.

Meanwhile, Djokovic dropped the first set against Zverev but stormed back on the strength of his serve and play on clutch points.

He chalked up 23 aces and won 72 percent of points on his first serve. Most importantly, he converted on six of his nine break-point chances, while his German counterpart went just 3-of-12 in those situations.

"After the first set I started moving better, playing better, I served extremely well," Djokovic said. "I think I had slightly more aces than him, which is a miracle for me against a big server like Sascha."

Karatsev, 27, had never qualified for a Grand Slam tournament and entered the Australian Open ranked No. 114 in the world. Now he's a couple victories away from one of the most unexpected major triumphs in history.

His aggressive approach has paid off on the fast courts of Melbourne Park. He finished the upset of Dimitrov, a three-time major semifinalist, with a sizable advantage in winners (34-21) and he earned eight breaks of serve to overcome 44 unforced errors.

While he'll be a massive underdog against Djokovic, it's the opportunity of a lifetime.

Here's a look ahead to Wednesday's quarterfinal matches:

Men's Bracket

(2) Rafael Nadal vs. (5) Stefanos Tsitsipas

(4) Daniil Medvedev vs. (7) Andrey Rublev

Women's Bracket

(1) Ashleigh Barty vs. Karolina Muchova

(22) Jennifer Brady vs. Jessica Pegula

Barty and Muchova will kick things off at 11 a.m. in Melbourne (7 p.m. ET Tuesday in the U.S.).