How one of tennis' greatest rivalry-friendship stories started: When then-17-year-old Rafael Nadal sat in Roger Federer's box at Indian Wells in 2004

Roger Federer and Rafael Nadal have shared a fabled rivalry for nearly two decades now. While their on-court duels have consistently evoked gasps of amazement in viewers, perhaps it is their off-court camaraderie that has stood out since the frequency of their encounters has reduced.

While it is rare to find such an intimate relationship between two of the greatest players in a particular sport. The Swiss and the Spaniard have shared a good relationship ever since they first crossed paths on the ATP tour. In fact, there was an instance when Nadal appeared in Federer's box and supported the Swiss during his match.

The incident dates back to the spring of 2004 - when the duo were fresh into their singles rivalry. The word singles plays an indispensable role here. Unbeknownst to the vast majority of their fans, it was in the doubles discipline that Federer and Nadal took on each other for the first time in their careers - on 17 March 2004 in the second round of Indian Wells.

The then World No. 1 had compatriot Yves Allegro as his doubles partner while the 17-year-old Spaniard teamed up with his own countryman, Tommy Robredo. The Spanish duo ended up winning the match 5-7, 6-4, 6-3.

While the Spaniard was eliminated by Agustin Calleri in the third round in singles, the 22-year-old Swiss progressed past the round of 16 without dropping a set. In the following round, as the 22-year-old Swiss took to the court against Juan Ignacio Chela, the Mallorcan teenager was spotted sitting in his box, a couple of seats away from his wife, Mirka.

How did Rafael Nadal come to be in Roger Federer's box?

Roger Federer and Rafael Nadal share a moment during the 2019 Laver Cup

Asked about the story behind the incident, the Swiss player could not recount much. He vaguely recalled having an exchange of words with Nadal at the conclusion of their doubles encounter, which followed them to the locker room. He believes it was then that he might have invited the Spaniard to watch his quarterfinal match from his own box - which the Spanish teenager accepted.

A couple of weeks later, the 'Fedal' rivalry ensued in Miami. The pair have since wielded distinctly contrasting games against each other to create some of the most spectacular moments in tennis. But there's a beautiful underlying friendship that elevates their rivalry beyond statistics. And perhaps that all began with a simple invite for one to the other player's box.