Related news: Mallorca tennis legend Rafa Nadal has earned $31.4 million so far this year

Former world number one Roger Federer retained his place at the top of the list of the world's highest paid tennis players for a 17th year despite not playing a match for nearly 14 months, Forbes has revealed.

Federer, 41, has not featured since Wimbledon last year after he had another operation on his knee, which has bothered the Swiss great in the twilight of his career.

However, the 20-times Grand Slam champion still raked in an estimated $90 million before taxes and agents' fees over the last 12 months to top the list, with the money coming from "endorsements, appearances and other business endeavours".

Japan's Naomi Osaka , who has won four majors, is second on the list after making around $56.2 million in the past year.

The 24-year-old launched a new media company in partnership with four-times NBA champion LeBron James and a new sports agency in June.

She is the highest-paid female tennis player, earning more than 23-times Grand Slam winner Serena Williams , who is set to retire after the U.S. Open that begins next week.

Williams has earned $35.1 million this year, edging former men's number ones Rafa Nadal ($31.4 million) and Novak Djokovic ($27.1 million).

U.S. Open champion Emma Raducanu made her debut on the list after she shot to stardom last year when she became the first qualifier in the Open Era to capture a Grand Slam title.

The British teenager is sixth on the list with $21.1 million while men's U.S. Open champion and world number one Daniil Medvedev is seventh with $19.3 million. Kei Nishikori ($13.2 million) and Venus Williams ($12 million) are eighth and ninth while Spanish sensation Carlos Alcaraz ($10.9 million) rounds off the top 10.

In the meantime, top seed Daniil Medvedev will open his U.S. Open title defence on Monday against American Stefan Kozlov but faces major hurdles on the path to a second Grand Slam title at Flushing Meadows, including in-form Australian Nick Kyrgios .

While Medvedev will not be looking too far ahead, fans certainly will at the prospect of an enthralling fourth-round showdown between the Russian and Wimbledon finalist Kyrgios who beat the world number one in three sets in Montreal this month.

The bottom half of the draw also throws up a potential mouth-watering all-Spanish clash between second seed Rafa Nadal , bidding for a fifth U.S. Open crown, and teenager Carlos Alcaraz , who last year became the youngest man to reach the quarter-finals at Flushing Meadows.

Nadal, who could leave New York with the world number one ranking if he can lift a 23rd Grand Slam trophy, will meet Australian Rinky Hijikata in the first round while third seed Alcaraz takes on Argentine Sebastian Baez.

Also standing in his way are seventh seed Cameron Norrie , the top-ranked Briton who faces an opening clash against France's Benoit Paire, and ninth seed Andrey Rublev. Greek fourth seed and Monte Carlo winner Stefanos Tsitsipas has never got past the third round at Flushing Meadows but may run into last year's Wimbledon finalist Matteo Berrettini in the fourth round if he can find his form on the famed blue courts.

French Open finalist Casper Ruud could land on the wrong side of the home crowd in his quarter, with top American and Indian Wells winner Taylor Fritz a potential fourth-round opponent.

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