Roger Federer is once again the highest-earning tennis player and Rafael Nadal is once again the second-highest, according to Forbes. The magazine, which annually estimates the earnings of the world's top athletes, has Federer earning $56.5 million over the previous 12 months, which puts him at No. 7 overall.

Nadal earned $44.5 million, putting him at No. 9. Boxer Floyd Mayweather, with $105 million, was No. 1, followed by soccer player Cristiano Ronaldo, with $80 million.

A year ago, Federer was ranked No. 2 overall with earnings of $71.2 million. This year, Federer earned $4.5 million in prize money and $52 million in endorsements, with Nadal earning $14.5 million in prize money and $30 million in endorsements.

Novak Djokovic was No. 17 with $33.1 million, $12.1 million in prize money and $21 million in endorsements.

The only three women to crack the top 100 were all tennis players. Maria Sharapova was the highest female athlete with a ranking of No. 34, counting $24.4 million in earnings, of which $22 million were endorsements. Li Na was No. 41, with $18 million in endorsements. Serena Williams was ranked 55, with $11 million in endorsements.