Dominic Thiem is climbing up the rankings while Kei Nishikori is set to return to action for the first time in 2020.

AFP Sport looks at this week's tennis talking points:

Thiem moves past Federer

He may still be waiting to join the 'Big Three' as a Grand Slam winner, but at least Dominic Thiem now has the consolation of breaking the stranglehold on the rankings enjoyed by Novak Djokovic, Rafael Nadal and Roger Federer.

On Monday, Australian Open runner-up Thiem reached a career high of three in the world, knocking Federer down a spot. The 26-year-old Austrian didn't play last week but he went past Federer when the Swiss star was unable to defend his points gained by winning the Dubai title last year.

Federer, 38, has undergone knee surgery and is not expected back on tour until the grass court season.

Djokovic, Nadal step up title chase

Djokovic won his fifth Dubai title while Nadal swept to a third victory in Acapulco although both men still have some way to go to reach the all-time record.

Djokovic now stands on 79 career trophies and Nadal has 85. Ivan Lendl won 94 while Federer has 103, six behind Jimmy Connors' leading 109 titles.

Empty feeling on Nishikori return

Former world number four Kei Nishikori makes his return to the sport for the first time since the US Open last year when he leads Japan in the Davis Cup qualifier at home to Ecuador this weekend.

However, due to fears over the coronavirus, the Friday-Saturday tie in Miki will be played behind closed doors. Nishikori has been sidelined after undergoing elbow surgery.

Sabalenka dedicates win to later father

Aryna Sabalenka won her sixth career title in Qatar by beating Petra Kvitova 6-3, 6-3 and dedicated victory to her father Sergey who died in November.

"I just lost my dad in the pre-season and he was my biggest motivation, and I'm doing it for him," said the 21-year-old from Belarus.

Clijsters steps up second comeback

Four-time major winner Kim Clijsters steps up her second comeback by playing on a wildcard at Monterrey this week.

The 36-year-old played her first match in over seven years in Dubai last month where she was defeated by Garbine Muguruza.

Still unranked, Clijsters has been drawn to face second seed Johanna Konta in the first round in Mexico. "I feel like with the tennis that I've been playing, I'm improving," she told wtatennis.com. "I still have a good level in me. I'm still at the stage where I feel like I need match rhythm."

Latest rankings:

ATP

1. Novak Djokovic (SRB) 10,220 points

2. Rafael Nadal (ESP) 9,850

3. Dominic Thiem (AUT) 7,045 (+1)

4. Roger Federer (SUI) 6,630 (-1)

5. Daniil Medvedev (RUS) 5,890

6. Stefanos Tsitsipas (GRE) 4,745

7. Alexander Zverev (GER) 3,630

8. Matteo Berrettini (ITA) 2,860

9. Gael Monfils (FRA) 2,860

10. David Goffin (BEL) 2,555

WTA

1. Ashleigh Barty (AUS) 8,717 points

 2. Simona Halep (ROU) 6,076

3. Karolina Pliskova (CZE) 5,205

4. Bianca Andreescu (CAN) 4,555

5. Sofia Kenin (USA) 4,365

6. Kiki Bertens (NED) 4,335

7. Elina Svitolina (UKR) 4,301

8. Belinda Bencic (SUI) 4,010 (+1)

9. Serena Williams (USA) 3,915 (-1)

10. Naomi Osaka (JPN) 3,625