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Roger Federer (left) and Rafael Nadal (right) are the two most successful tennis stars of the Open Era. Lintao Zhang/Getty Images

Roger Federer and Rafael Nadal have enjoyed stellar careers as the No. 1 and No. 2 leaders in Grand Slam titles, respectively. The two tennis legends have a combined 37 Grand Slams and 177 total titles, therefore they've taken home a considerable amount of prize money.

Combined the rivals have earned more than $218 million over their careers.

Federer, who made his professional debut in 1998, is closing in on $117 million in career earnings. The 36-year-old has earned just over $5 million in 2018 after skipping the French Open.

Nadal debuted in 2001 at age 15 and has $101.3 million in career prize money. The world No. 1 has outperformed Federer in 2018, earning $6.7 million.

The U.S. Open may decide who finishes 2018 with the most prize money. The winner will receive $3.8 million.

Nadal is the defending U.S. Open champion but oddsmakers have given him 9/2 odds of repeating, trailing both Novak Djokovic (3/1) and Federer (4/1), according to betting site OddsChecker.com.

Nadal has won three U.S Open titles, while Federer has won five, but his last title at Flushing Meadows came in 2008.

Federer has compiled a 29-4 record in 2018 after winning the Australian Open, the Rotterdam Open and the grasscourt Stuttgart Open. Nadal has a 35-3 record this year, having dominated the clay-court season with wins at the Monte Carlo Open, Barcelona Open, the Italian Open and his 11th French Open.

The two tennis legends will see another windfall in November when they compete in the ATP Finals at O2 Arena in London. Total prize money for the eight-player tournament is $8 million with the undefeated champion standing to win $2.7 million.

Interestingly, Federer and Nadal haven't faced each other since the Shanghai Open in October 2017. Federer prevailed, 6-4 6-3.

On another note, Nadal has an edge on Federer in doubles. Nadal has won 11 career titles, while Federer has won eight.