The two best men's players in the world are reconfiguring the sport before their opponents' eyes. They don't know what to do about it

The first round of the Australian Open continues on Monday at Melbourne Park where top seed and defending champion Jannik Sinner seeks a third Grand Slam title while Novak Djokovic begins his quest for a record-extending 25th major.

When Carlos Alcaraz is on court for a training session, perhaps working on his newly revamped service motion, he’s doing so to buttress a game already good enough to claim four Grand Slam titles