The Australian Open has produced an opening week of upsets, with four of the Top 10 seeds falling before the fourth-round stage. With the pressure mounting, Stefanos Tsitsipas and Felix Auger-Aliassime will look to overcome tricky tests against Jannik Sinner and Jiri Lehecka, respectively, and stay alive in Melbourne on Sunday.
ATPTour.com looks at what to watch on Day 7 as players look to reach the quarter-finals.
 Stefanos Tsitsipas (GRE) vs.  Jannik Sinner (ITA)
Tsitsipas is the highest seed left in the draw, following Rafael Nadal and Casper Ruud’s early exits. Despite seeds tumbling around him, the Greek has had no such problems, not dropping a set en route to the fourth round.
The third seed, who is a three-time semi-finalist in Melbourne, will be motivated to keep his run going as he plays for a double prize this fortnight. If Tsitsipas wins his maiden major title, he will rise to No. 1 in the Pepperstone ATP Rankings for the first time.
His focus will be on Sinner, though, who is set to be a tricky customer for the World No. 4. The 15th-seeded Italian advanced in straight sets in his opening two matches before he demonstrated his fighting spirit against Marton Fucsovics, rallying from two-sets-to-love down to take out the Hungarian.
In a battle between two Next Gen ATP Finals champions, Sinner will look to gain revenge against Tsitsipas, having lost to the Greek in the quarter-finals in Melbourne last year.
“I have a good memory from last year,” said Tsitsipas, who leads Sinner 4-1 in their ATP Head2Head series. “I’m sure he’s much better prepared this time. I hope I can deliver a good sort of level of game because it was close last time.
“It’s about maintaining that. It’s about building within that. It’s about perhaps maybe sticking to what worked previously, and continually adding to it when out there in the match.”
 Felix Auger-Aliassime (CAN) vs Jiri Lehecka (CZE)
Auger-Aliassime reached the quarter-finals in Melbourne last year. The 22-year-old will aim to match that feat when he takes on the 2022 Next Gen ATP finalist runner-up Lehecka on Margaret Court Arena.
The Canadian enjoyed a standout 2022, lifting four tour-level titles. However, his path to the fourth round at the first major of the season has been far from easy. Auger-Aliassime has dropped four sets across his opening three matches, battling past Vasek Pospisil, Alex Molcan and Francisco Cerundolo.
Lehecka is set to provide another stern test, having upset Borna Coric and Cameron Norrie en route to his maiden fourth round appearance at a major. The 21-year-old, up to No. 51 in the Pepperstone ATP Live Rankings, is relishing the chance to play Auger-Aliassime.
“I’m very excited because for me to play all these guys, it’s the reason why I play tennis,” Lehecka said looking ahead to his first meeting against the sixth seed. “It was always my dream to win the big matches at a Grand Slam. To have a chance to play on the biggest stages. It’s a dream come true for sure. But on the other hand, I know that I have the level to beat these guys. I know that my game fits me well for conditions over here.”
 Hubert Hurkacz (POL) vs.  Sebastian Korda (USA)
Sebastian Korda produced one of the performances of his career when he upset two-time Australian Open finalist Daniil Medvedev in the third round. The American will aim to back that up when he meets Hubert Hurkacz on Rod Laver Arena, with Korda eyeing a first quarter-final appearance at a major.
While Korda has yet to drop a set in Melbourne, Hurkacz has been pushed to the brink. The 10th seed came back from two sets to one down against Lorenzo Sonego in the second round and Denis Shapovalov in the third round. Seeking his second Grand Slam quarter-final, the 25-year-old will aim to make a faster start against Korda.
Hurkacz takes a 1-0 ATP Head2Head series lead into their meeting, having defeated the 22-year-old in the Delray Beach final in 2021.
 Karen Khachanov vs  Yoshihito Nishioka (JPN)
Karen Khachanov reached the semi-finals at the US Open in September and is now two wins away from matching that achievement in Melbourne. The 18th seed defeated American Frances Tiafoe to set a fourth-round meeting against Japan’s Yoshihito Nishioka.
The 33-year-old Nishioka has been perfect so far in Melbourne, not dropping a set to reach the fourth round at a major for the first time. Nishioka will aim to continue that run against Khachanov, who leads the 31st seed 2-1 in their ATP Head2Head series.