Robeisy Ramirez’s optional opponent stood 6-foot-1, highly unusual for featherweights.

Rafael Espinoza still wasn’t supposed to be this tall of an order for the heavily favored former WBO 126-pound champion December 9. It was evident early in their 12-round title fight, though, that the relentless Espinoza posed problems for Ramirez that the Cuban southpaw didn’t anticipate in what emerged as BoxingScene.com’s 2023 “Upset of the Year.”

As the previously underexposed Espinoza (24-0, 20 KOs) threw a lot of punches at Ramirez and landed numerous right uppercuts during the first four rounds, Ramirez realized that he was in for quite a fight, something that could jeopardize a potential showdown with Japanese superstar Naoya Inoue in 2024.

Down on the scorecards, the ex-champion made their fight interesting when Ramirez’s right hook dropped Espinoza with five seconds to go in the fifth round. Ramirez caught Espinoza while he was switching stances and looked like he might knock out a formidable foe he entered the ring as a 16-1 favorite to beat.

Ramirez controlled the action over the next three rounds to close the gap on the scorecards.

He buzzed Espinoza again with a left hand that landed with just under 30 seconds to go in the seventh round. Another left by Ramirez staggered Espinoza barely 20 seconds into the eighth round.

By then, it appeared as if Ramirez would recover from his slow start and retain his WBO featherweight title. A rejuvenated Espinoza rallied during the final three rounds and got the boost he needed when his right-left combination made Ramirez (13-2, 8 KOs) take a knee with 26 seconds to go in the 12th round.

Judge Efrain Lebron scored their back-and-forth fight a draw, 113-113, but judges Benoit Roussel (114-112) and Steve Weisfeld (115-111) credited Espinoza for winning a main event ESPN aired from Charles S. Dodge City Center in Pembroke Pines, Florida.

And just like that, Mexico’s Espinoza evolved from an unknown underdog into a world champion.

“I knew that I had to drop him in order to win,” Espinoza said. “I just put my heart into it. I always do that. And thank God it happened.”

Espinoza exceeded even his own expectations based on what fans didn’t know occurred early in the Guadalajara native’s fight with a two-time Olympic gold medalist.

“I think I’ve had a broken foot since the second round,” Espinoza said. “But what kept me on my feet was my daughter, my parents, my wife and my family. I knew that all of Mexico was watching me. And I knew that I had to become a world champion.”

RUNNERS-UP (listed chronologically)

Liam Smith over Chris Eubank Jr.

Eubank was a 3-1 favorite and hadn’t been beaten inside the distance when he met Smith in their first domestic clash January 21 at AO Arena in Manchester, England. Smith surprisingly overpowered the usually durable Eubank, whom he hurt with a right hand and dropped with a left hook 45 seconds into the fourth round. Brighton’s Eubank got up, yet he never got his legs back under him before Liverpool’s Smith sent him to the canvas again and referee Victor Loughlin halted the action. Eubank (33-3, 24 KOs) avenged his defeat in their rematch September 2 at AO Arena, where he dominated Smith (33-4-1, 20 KOs) on his way to a 10th-round, technical-knockout win.

Brian Mendoza over Sebastian Fundora

The first six rounds of their fight unfolded as the 9-1 odds suggested. Mendoza was shut out on two scorecards (60-54, 60-54) and had won one round on the other card (59-55) when they entered the fateful seventh round April 8 at Dignity Health Sports Park in Carson, California. That’s when Albuquerque’s Mendoza hammered the 6-foot-6 southpaw with a left hook and quickly, violently followed up with a right-left combination that flattened Fundora (20-1-1, 13 KOs. The dazed Coachella, California native couldn’t get up and referee Ray Corona counted him out. Mendoza (22-3, 16 KOs) won the WBC interim super welterweight title and positioned himself to challenge WBO junior middleweight champ Tim Tszyu in his following fight.

Zhilei Zhang over Joe Joyce

London’s Joyce was undefeated and the mandatory challenger for Oleksandr Usyk’s WBO heavyweight title when he squared off against Zhang on April 15 at Copper Box Arena in London. The 6-foot-6, 278-pound Zhang continually caught the defensively deficient Joyce with left hands that eventually closed his right eye in the sixth round, which prompted referee Howard Foster to stop their fight. Joyce (15-2, 14 KOs) exercised the immediate rematch clause in his contract, but China’s Zhang (26-1-1, 21 KOs) knocked him out even earlier in their second contest. Zhang’s right hook knocked Joyce out late in the third round September 23 at OVO Arena Wembley in London.

Agit Kabayel over Arslanbek Makhmudov

Germany’s Kabayel entered the ring undefeated December 21 at Kingdom Arena in Riyadh, Saudi Arabia. Russia’s Makhmudov, considered the bigger puncher, was still a 14-1 favorite to win this battle between unbeaten heavyweights on the Anthony Joshua-Otto Wallin undercard. Kabayel’s speed and accuracy troubled his taller, heavier opponent, though, and enabled Kabayel (24-0, 16 KOs) to drop Makhmudov three times, all with body shots, in the fourth round. Referee Steve Gray stopped their 10-rounder after Makhmudov (18-1, 17 KOs) went down for the third time, at 2:03 of the fourth round.

Joseph Parker over Deontay Wilder

Alabama’s Wilder was consistently favored by a 7-1 margin to beat Parker and move forward to a long-awaited showdown with Joshua. After boxing less than one round over the previous two years, the knockout artist never let his hands go, was wary of Parker’s power and got out-worked by the opportunistic former WBO champion. New Zealand’s Parker (34-3, 23 KOs) won their 12-round bout so decisively on the scorecards December 21 in Riyadh, critics of Wilder (43-3-1, 42 KOs) have suggested that the 38-year-old former WBC champ seems as though he doesn’t want to fight anymore. Parker, meanwhile, rejuvenated his career and put himself in position to secure another significant fight almost 15 months after Joyce knocked him out in the 11th round.

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