As he prepares to take the court for the final time as a professional tennis player in the 2024 Davis Cup in his native country of Spain, 22-time major champion Rafael Nadal received a heartfelt tribute from his longtime rival and dear friend, Roger Federer.

Federer, a 20-time major champion who in September of 2022 retired from tennis, paid homage to Nadal in a lengthy post on his account on X (formerly Twitter) on Tuesday, beginning by acknowledging the competitiveness between the two—and the great lengths he went in his quest to defeat the Spaniard.

“As you get ready to graduate from tennis, I’ve got a few things to share before I maybe get emotional,” Federer wrote. “Let’s start with the obvious: you beat me—a lot. More than I managed to beat you. You challenged me in ways no one else could.”

“On clay, it felt like I was stepping into your backyard, and you made me work harder than I ever thought I could just to hold my ground. You made me reimagine my game—even going so far as to change the size of my racquet head, hoping for any edge.”

Federer and Nadal, who met 40 times in their career on the tour with Nadal holding a 24-16 edge, forged a great rivalry that produced some of the most gripping tennis matches in the sport’s history, most notably, the 2008 Wimbledon final, a five-set epic won by Nadal and widely considered one of the greatest matches of all-time.

But, the two also developed a beautiful friendship, which was on full display multiple times throughout their careers, whether the two tennis greats were attempting to shoot a promotional video in 2010 and could barely produce a television-worthy take because they were laughing so hard, or, more recently, barely holding it together and breaking down to tears on the court for Federer’s final match with Team Europe at the Laver Cup.

“And then there was London—the Laver Cup in 2022,” Federer wrote. “My final match. It meant everything to me that you were there by my side—not as my rival but as my doubles partner.”

“Sharing the court with you that night, and sharing those tears, will forever be one of the most special moments of my career.”

Nadal, 38, announced he would be retiring from tennis in a video posted onto X in October. The Spaniard won the second-most majors (22) in men’s tennis history, including a record 14 French Open singles titles. He is one of just three men, along with Andre Agassi and Novak Djokovic, to win the golden slam (all four grand slam singles titles and a gold medal in a career).

Nadal will face Botic van de Zandschulp in the Davis Cup quarterfinals at 11 a.m. ET.