Lucero’s lack of defense and sluggishness instead turned it into the worst experience of the Mexican contender’s career. Unknown Argentinean underdog Ismael Flores often took target practice on the stationary Lucero and upset him by unanimous decision on the David Benavidez-Gilberto Ramirez undercard.

The 27-year-old Lucero (18-1, 14 KOs), who went off as a 9-1 favorite, according to DraftKings, relied on an iron chin to make it to the end of their 10-round bout. He rarely moved his head, though, and never hurt Flores, even though Lucero was on a seven-fight knockout streak going into the bout.

Judge David Sutherland scored it 99-91 for Flores (18-1-1, 12 KOs). Cory Santos and Steve Weisfeld had it 98-92.

“My rival was the better man tonight,” Lucero said. “He came to steal the night and came with everything. I have no excuses for tonight. I had a great preparation and I just fell short. The better man won.”

Lucero was initially scheduled to face fellow Mexican Alan Sandoval (30-0-1, 19 KOs). Flores replaced Sandoval on two weeks’ for undisclosed reasons, however, and capitalized on the most meaningful opportunity of his career.

Well aware he desperately needed a knockout, the mostly listless Lucero attacked Flores to start the 10th round. Flores took his best shots, taunted Lucero as he moved away from him and looked content to coast to victory before Flores unloaded a flurry of punches on the unsuspecting Lucero toward the end of the final round. Lucero didn’t fight with much urgency in the seventh, eighth and ninth rounds, even though it was very obvious he would need a knockout to win.

A more offensive-minded Lucero took fewer punches in the fifth and sixth rounds, when Flores was less active. But he couldn’t build on the momentum he established in the fourth round.

Lucero finally took the fight to Flores in the fourth round, when he backed up an opponent who appeared tired and landed right hands and left hooks as Flores backed into the ropes.

One of Flores’ shots opened a cut around Lucero’s right eye in the third round. Lucero didn’t take as many hard shots during the third round as he did in the first six minutes of action, but he also hadn’t found a rhythm offensively.

Lucero never seemed affected by any of Flores’ punches in the surprisingly one-sided first or second rounds, but he allowed Flores to build his confidence and an early lead on the cards.

American super middleweight prospect Daniel Blancas beat Raul Salomon by unanimous decision in the final fight before the pay-per-view portion of the Benavidez-Ramirez undercard began.

Milwaukee’s Blancas (15-0, 7 KOs) dealt well with the Mexican veteran’s pressure throughout their 10-round bout, countered at times as Salomon came forward and out-boxed him. Judge Eric Cheek scored it a shutout for Blancas, who won 100-90 on his card. Judges Kermit Bayless and Max De Luca scored nine rounds apiece for Blancas, 99-91 on each of their cards.

Salomon slipped to 16-4-1 (14 KOs), but he hasn’t been knocked out in five years as a pro.

Teenage lightweight prospect Dylan Capetillo picked apart an opponent exactly twice his age in a four-round round bout before Blancas’ victory.

Las Vegas’ Capetillo (2-0, 1 KO), the 17-year-old son of veteran trainer Jorge Capetillo, beat Omaha, Nebraska’s James Pierce (2-1, 2 KOs) by the same score, 39-37, according to Cheek, Lisa Giampa and Patricia Morse Jarman. Capetillo consistently connected with straight rights on his left-handed opponent, and barely got hit until the final minute of a fight the younger, faster, sharper fighter comfortably controlled.

Colombian light heavyweight Juan Carlos Carrillo knocked out Ecuador’s Marlon Delgado toward the end of the fourth round of a bout between unbeaten prospects that opened Prime Video’s preliminary coverage of the undercard.

Carrillo (15-0, 11 KOs), a 2016 Olympian, pushed Delgado to the canvas with 13 seconds to go in the fourth round. As soon as a fatigued Delgado (8-1, 6 KOs) reached his feet and the action continued, Carrillo landed a right to his body that sent Delgado to the canvas again.

Delgado couldn’t get up before referee Thomas Taylor counted him out. The official time of the stoppage was 2:59 of the fourth round.