DAVIS, Calif. — One slouchy, soft-spoken teenager will be conspicuously absent in Gwangju, South Korea, when the world’s best swimmers audition to replace the retired Michael Phelps in his franchise event, the 200-meter butterfly.

Gianluca Urlando, a 17-year-old American who wasn’t alive when Phelps’s global reign began in 2001, last month recorded a faster time in the event than Phelps clocked to break his own world record at the same age. The effort vaulted Urlando to third in the 2019 world rankings, more than two seconds ahead of his next-fastest American rival.

“The kid has talent,” Phelps, a three-time Olympic champion in the event, said of Urlando, who will be wrapping up summer school in his hometown, Sacramento, when the first two rounds of the 200-meter butterfly are contested Tuesday at the World Championships.

“Honestly, I’d love to be going to Korea,” Urlando said after a workout this month.

Urlando, who goes by Luca, is one of the rising stars affected by U.S.A. Swimming coaches’ collective decision not to approach the World Championships as an Olympic dress rehearsal. Another is Regan Smith, a 17-year-old who sat out the 100-meter backstroke Monday despite clocking a time last month that was a second faster than either of the two American entrants posted in the preliminaries.