Dmitry Tursunov was a pretty decent tennis player in his day, rising to a career-high No.20 on the ATP Tour in 2006.

Today? Let’s just say he’s not quite the athlete he used to be. When he’s practicing with Belinda Bencic, we can report that the ball sometimes gets past him.

“Acing him,” Bencic told reporters at the Australian Open, “it’s just standard routine. I do that every practice against him, and he cannot read my serve, and he’s also returning really bad.”

Fortunately for Tursunov, he has a side hustle -- he’s one of the most successful coaches in the game. He’s been working with Bencic since last October and the early results have been impressive.

He mentored Aslan Karatsev as a teenager, coached Elena Vesnina, more recently Anett Kontaveit and, briefly, Emma Raducanu. Oh, and for two years on and off -- from June 2018 to August 2020 -- he helped Aryna Sabalenka become the dynamic player she is.

This is relevant -- and deliciously dramatic -- because Bencic on Monday meets Sabalenka, the two winners of the two events in Adelaide earlier this month, in a fourth-round match.

“Dmitry was her coach before,” Bencic said, “so he can help me a lot, I hope.”

More from Day 7:

It’s one of four enticing matches from the bottom half of the draw. A breakdown:

No.5 Aryna Sabalenka vs. No.12 Belinda Bencic

Bencic was a 6-2, 7-5 third-round winner over Camila Giorgi, her eighth win in nine matches this season. She defeated two Top 10 players on the way to the title in Adelaide -- No.4 Caroline Garcia and No.8 Daria Kasatkina -- and that result returned her to the Top 10.

Australian Open: Scores | Draw | Order of play

Now she’s up against another Top 10 player in Sabalenka, who in the last round was a 6-2, 6-3 winner against Elise Mertens. Sabalenka won the other tournament hosted in Adelaide and is a snazzy 7-0 on the year.

Australian Open: Bencic moves into second week for first time since 2016

“She’s a great fighter, a great player, moving well, hitting the ball quite clean,” Sabalenka said of Bencic. “Yeah, she’s in good shape, as well. I think it’s about first few shots. I feel like I have to stay really aggressive in the first few shots, and then the easy, shorter ball will come.”

They’ve played only twice before, with Sabalenka taking a New Haven quarterfinal win in 2018 and Bencic prevailing a year later in Dubai -- in a third-set tiebreak. The winner will find herself in the quarterfinals at Melbourne Park for the first time.

Like all good coaches, Tursunov is a truth-teller, according to Bencic. 

“Tells you what you need to hear, and sometimes you really need to hear the uncomfortable stuff,” Bencic said. “He just pushes me a lot, so it puts me out of my comfort zone. It’s working so far, so I’m definitely trusting him a lot. I just feel like we have a great year in front of us.”

No.4 Caroline Garcia vs. Magda Linette

Garcia has won more matches than any other player on the Hologic WTA Tour since last June, but in the third round she fell into a quick one-set deficit against Laura Siegemund.

“I couldn’t really find my rhythm,” Garcia told reporters later. “She was reading my game pretty well. Yeah, not to panic. Even if you play some bad tennis, you have to try until the end, try to fight, try to find the solution, push the ball back in the court, whatever, but just do something different.”

Garcia did just that and won the last two sets comfortably. She’s a robust 6-1 in this new year. She’ll be tested by Linette, who upset No.19 seed Ekaterina Alexandrova 6-3, 6-4. It was the Polish player’s seventh Top 20 win, including a second-rounder over No.16 seed Anett Kontaveit.

At the age of 30, she’s reached the final 16 of a Grand Slam for the first time. Linette lost the only meeting between these two, but that was five years ago in Strasbourg.

No.23 Zhang Shuai vs. No.30 Karolina Pliskova

Zhang celebrated her birthday with a 6-3, 6-2 victory over qualifier Katie Volynets. At 34, Zhang is the oldest player left in the draw -- and she’s never been better. She’s playing at a career-high ranking of No.22 and is looking to advance to a major quarterfinal for only the third time.

Pliskova, a former World No.1 and two-time Grand Slam finalist, was a 6-4, 6-2 winner over Varvara Gracheva. She was forced to withdraw from last year’s Australian Open with an injury to her right hand and didn’t play her first match until March. It took Pliskova quite some time to return to form.

She was forced to qualify for the second event in Adelaide but lost to Danielle Collins in the first round. The conditions in Melbourne Park, however, suit Pliskova, and she’s won her three matches in straight sets. A fact that bears watching: Pliskova has won all 22 of her matches at the Australian Open when she wins the first set.

Pliskova has won all seven of the matches these two have played. For what it’s worth, the last one came nearly five years ago in Indian Wells.

Donna Vekic vs. Linda Fruhvirtova

When Vekic was a 6-2, 6-2 winner over Nuria Parrizas Diaz, she joined a select circle. After a 3-0 run for Croatia at the United Cup and another 3-0 jaunt in Melbourne, Vekic is one of only two undefeated players in 2023 remaining in the draw: Sabalenka and the No.64-ranked Vekic.

Fruhvirtova, ranked No.82, is another surprise. She defeated Marketa Vondrousova in three sets after Vondrousova took out No.2 seed Ons Jabeur. At the age of 17, Fruhvirtova is the youngest player remaining in the draw. Her first major came last year at the US Open.

These two have never played -- and this is the only one of eight fourth-round matches that is seedless.