LAS VEGAS – Ernesto “Tito” Mercado emphatically introduced himself to the uninitiated Saturday night.

The hard-hitting junior welterweight prospect landed a devastating left-right combination that knocked out former two-division champion Jose Pedraza in the fourth round of their scheduled 10-rounder at The Cosmopolitan of Las Vegas. Pedraza got off his back and beat referee Robert Hoyle’s count, but he couldn’t stand up straight and Hoyle wisely waved an end to a bout DAZN streamed as part of the Diego Pacheco-Steven Nelson undercard.

The official time of the stoppage was 2:08 of the fourth round.

The 23-year-old Mercado, of Pomona, California, improved to 17-0 and produced his 16th knockout. Pedraza, a former IBF junior lightweight and WBO lightweight champ, was the most experienced opponent of Mercado’s three-year pro career, though well past his prime.

“I think he thought I was gonna try and knock him out, waste my energy,” Mercado told DAZN’s Chris Mannix after making a successful debut for promoter Matchroom Boxing. “But I was just staying calm, man, hitting the body, picking my shots right, and then when I saw the perfect shot I took him out.”

The 35-year-old Pedraza (29-7-1, 14 KOs), of Cidra, Puerto Rico, fought for the first time since unbeaten lightweight contender Keyshawn Davis (12-0, 8 KOs, 1 NC) stopped him in the sixth round of their fight last February 8 at Mandalay Bay’s Michelob ULTRA Arena.

Pedraza managed to avoid many of Mercado’s hardest shots during the second and third rounds, before he unloaded the combination that abruptly ended the opener of DAZN’s three-fight stream. Pedraza protected himself well for much of the first round, when an assertive Mercado let his hands go and made him cautious.

“He was scared, man,” Mercado said. “He was scared to get caught with a good shot. With these other fighters that got no power, like Keyshawn, someone like Shakur, he [wouldn’t] do the same thing. He would throw a lotta punches. But with me, he don’t wanna do none of that.”