Lorenzo Musetti is only the latest of many teens and early 20-somethings to shake things up on the ATP tour. Erik Jonsson (@erktennis) is a longtime Challenger and prospect watcher, and he shares his thoughts on Musetti, Aslan Karatsev, Jannik Sinner, Carlos Alcaraz, Sebastian Korda, and more. We talk about how to identify future tour-level stars by watching Challenger matches, whether there is any hope of another top-tenner as short as Diego Schwartzman, why Sweden hasn't produced a female tennis superstar, and what constitutes a legit top-20 player.