LOS ANGELES – Fernando Martinez reacted Thursday like a little kid unwrapping presents on Christmas morning.

Finally, more than seven months after his life-changing upset of Jerwin Ancajas, Martinez was presented with his IBF junior bantamweight championship belt before a press conference at The Westin Los Angeles Airport. Martinez, the father of a 9-year-old daughter, cradled his crown and joked that it felt like he had just witnessed the birth of his second child.

The Argentinean champion isn’t sure Ancajas appreciated that title as much as him before they fought February 26 in Las Vegas. The 31-year-old Martinez (14-0, 8 KOs) sensed that the Filipino southpaw underestimated him entering a 12-round, 115-pound title bout that Showtime televised from The Cosmopolitan.

“He underrated me, but I surprised everybody,” Martinez told BoxingScene.com through a translator. “Last time, I made his day sh!t.”

Ancajas was a 5-1 favorite on fight night, but Martinez out-threw and out-landed an ex-champion who is promoted by Manny Pacquiao’s company. An impressive Martinez won by large margins on all three scorecards (118-110, 118-110, 117-111).

The 30-year-old Ancajas (33-2-2, 22 KOs) was by far the best opponent of Martinez’s five-year, 14-fight professional career. The previous five fighters he defeated had a combined record of 56-46-9, but Martinez credited his superior preparation for helping him end Ancajas’ five-year championship reign.

“I think I surprised everybody,” said Martinez, who went 148-2 as an amateur boxer. “I don’t have a lot of professional fights, like other people, but I have a lot of experience in amateur fights. It was not an easy fight, but I studied him well before our fight.”

Martinez, who is co-promoted by Marcos Maidana’s company and Legacy Boxing, was contractually bound to an immediate rematch. He was an optional opponent for Ancajas, whose team wisely required a second fight if the 11th-ranked Martinez upset him.

The 30-year-old Ancajas claims that an improper weight cut caused cramping that hindered him for most of their 12-round fight. The former champion also denied that he overlooked his previously unknown opponent.

“I never underestimate any opponent,” Ancajas told BoxingScene.com, also through a translator. “I always respect my opponents. It’s just that my conditioning was a problem. I respect Martinez and I didn’t underestimate him.”

Regardless, Buenos Aires’ Martinez anticipates a more competitive fight in a rematch Showtime will televise as the opener of a three-bout broadcast from Dignity Health Sports Park in Carson, California (10 p.m. ET; 7 p.m. PT).

“Now we know each other,” said Martinez, who is consistently listed as nearly a 3-1 favorite to beat Ancajas again. “Maybe he studied me better. We’re two warriors and we’ll make a hard fight, but the winner will be the one who fights the more intelligent fight.”

Showtime will air two more 12-round title fights following the Martinez-Ancajas rematch.

Carlos Adames (21-1, 16 KOs), of Comendador, Dominican Republic, and Juan Macias Montiel (23-5-2, 23 KOs), of Los Mochis, Mexico, will square off in the co-feature for the WBC’s vacant interim middleweight title. In the main event, unbeaten southpaw Sebastian Fundora (19-0-1, 13 KOs), of Coachella, California, will defend his WBC interim super welterweight crown against Mexican contender Carlos Ocampo (34-1, 22 KOs).

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.