Swiss World No.1 Roger Federer is getting ready to defend his title at the BNP Paribas Open in Indian Wells, California, where the field is notable for the absences of Spain’s Rafael Nadal, Switzerland’s Stanislas Wawrinka, France’s Jo-Wilfried Tsonga and France’s Richard Gasquet.

The 36-year-old Federer, who has won the event in the California desert five times, is defending 1,000 ranking points in the Coachella Valley, where he defeated Wawrinka in last year’s championship match 6-4, 7-5, REPORTS eFE.

Federer, who has won a record 20 Grand Slam titles, will hang on to the No.1 spot in the ATP rankings if he makes it to the semifinals at Indian Wells.

If Federer falters at the year’s first Masters 1000 event, Nadal will retake the top spot in the rankings on March 19 despite being out of action with a hip injury.

Federer’s return to the No.1 spot came amid one of the most remarkable runs of his career.

The Swiss star dropped out of the top 15 in the rankings when a knee injury forced him to shut down his 2016 season prematurely, but he has made a phenomenal comeback since January 2017.

He won the Australian Open and Wimbledon last year and then extended his record haul of Grand Slam titles to 20 by successfully defending his Australian Open title in January.

The main threat to Federer at Indian Wells is expected to be Serbia’s Novak Djokovic, who is returning to action after undergoing elbow surgery.

Djokovic, whose ranking has fallen to No. 13 and is also a five-time BNP Paribas Open champion, was defeated by South Korea’s Hyeon Chung in the round of 16 at the Australian Open, the Serb’s first tournament since Wimbledon.

On the women’s side, all eyes will be on American Serena Williams, who is returning to competition after giving birth.

Williams, who has not played in a tournament in 14 months, won the 2017 Australian Open while pregnant.

The 36-year-old Williams lost an exhibition match to Latvia’s Jelena Ostapenko, the French Open champion, on December 30.

Among the other players in the draw at Indian Wells are World No. 1 Simona Halep, of Romania; defending champion Elena Vesnina, of Russia; Russian star Maria Sharapova; Denmark’s Caroline Wozniacki, who won the Australian Open; and Spain’s Garbiñe Muguruza, the reigning Wimbledon champion.

Indian Wells is offering a bonus of $1 million this year to the player who wins both the singles and doubles titles, a feat achieved by just six players: Roscoe Tanner, Boris Becker, Jim Courier, Lindsay Davenport (twice) and Vera Zvonareva.