LAS VEGAS — Boxing’s best-kept secret, a teenage prodigy whose sparring sessions have become the stuff of Las Vegas gym legend, is about to be unleashed. 

Julian “El Natural” Montalvo (3-0, 2 KOs) has inked a long-term promotional contract with Top Rank. The 17-year-old junior lightweight, a Las Vegas native whose family hails from Sinaloa, Mexico, will return this summer following his unanimous decision over Erick Eugenio Tovar Gutierrez last Saturday in Colima, Mexico.