Tennis quietly ended its age-old rule against on-court coaching this summer. The change comes at a cost, but the upside is worth it.

Both world No. 1s were among a slew of current top players and tennis legends who took to social media to celebrate the 20-time Grand Slam champion.

The 20-time Grand Slam champion also recalled his practice session with Alcaraz at Wimbledon—and why it was memorable for more than just a chance to get an early look at the future world No. 1.

The US Open champion immediately returned to action following his maiden major victory, winning one of two Davis Cup matches at the team competition.

A day after becoming the first man born in the 2000s to win a Grand Slam title, he became the first teenager to reach No. 1 in ATP rankings history.

The Canadian overcame the US Open champion, 6-7 (3), 6-4, 6-2, to pull his nation level at 1-1 with Spain in Friday's Group B showdown.

From Rafael Nadal to Iga Swiatek, the game's brightest lights paid tribute to the 20-time Grand Slam champion in the wake of his shock retirement announcement.

Alcaraz has played with Babolat racquets since 2013, and lifted his first major trophy last weekend when he defeated Casper Ruud in a four-set final.

The newly crowned world No. 1 is doing anything but slowing down after his US Open victory, as 'The Armada' takes on Serbia, Canada and South Korea in the group stage.

Carlos Alcaraz is the latest player to show that youth can be served at the Slams.