Rafael Nadal wished fellow tennis legend Roger Federer the best Thursday after Federer announced his retirement from the sport.

Nadal noted that while it is a "sad day" to see his "friend and rival" retire, he hopes Federer has nothing but happiness in retirement:

A few hours before Nadal's tweet, Federer announced his retirement on Twitter, thanking his family, peers, fans and the sport of tennis:

Federer is arguably the greatest men's tennis player of all time, but at age 41, injuries caught up to him and have prevented him from playing in any Grand Slam tournaments since reaching the quarterfinals at Wimbledon last year.

With 20 career Grand Slam titles during the Open Era, Federer is behind only Nadal and Novak Djokovic on the all-time list. Federer is also first for the most Wimbledon men's titles with eight.

Federer had many memorable matches and rivalries during his career, but none came close to matching what he and Nadal did together.

All told, Federer and Nadal faced each other 40 times, and Nadal holds a 24-16 advantage. Fourteen of those matches were in Grand Slam tournaments, and Nadal won 10 of them.

Federer managed two Wimbledon finals and one Australian Open final win over Nadal, though, and he defeated the Spaniard in their last match, which was in the semifinals at Wimbledon in 2019.

The Swiss star went on to lose a five-set thriller to Djokovic in what was the last Grand Slam final of his illustrious career.

While it is possible Djokovic will be considered the top player of all time, tennis was at one of its highest points when Federer and Nadal dominated the sport and faced each other on its biggest stages time and time again.

Federer's retirement is a sign that time may be getting short for Nadal as well, and it became even clearer at the U.S. Open that the young guns are starting to emerge as 19-year-old Carlos Alcaraz won the tournament.

A golden era in men's tennis is coming to an end, but the respect that two of its biggest stars have for each other will mean it's remembered fondly for years to come.