By Jake Donovan

In a very late entry for Upset of the Year, Mexico's Jose Argumedo pulled off a stunning - albeit debatable - split decision win over Katsunari Takayama on the road Thursday evening in Osaka, Japan. 

Scores were 87-84 (twice) in favor of Argumedo and 86-85 for Takayama, who was unable to continue after nine grueling rounds of action due to cuts over both eyes. Because both wounds were produced by headbutts, the bout went to the scorecards.

Argumedo entered the fight as a rare title challenger whose pro debut also came versus a former champ, having dropped a split decision to Oswaldo Novoa in 2011, the first of their three fight set. Argumedo ultimately 1-2 against his countryman, who would go on to become the unlikeliest of champions in claiming a strawweight belt with a knockout win over Chao Zhong Xiong on the road in China. 

In that same vein, Argumedo marched boldly into the Osaka hometown of Takayama, who entered the fight celebrating the one-year anniversary of his third tour as a strawweight titlist. A three-fight win streak had preceded the event, all coming after a 12-round decision loss to Francisco Rodriguez Jr., with their unforgettable thriller earning top honors as 2014 Fight of the Year.

A bounce-back 7th round knockout win over Go Aidara last New Year's Eve allowed the veteran boxer to ring in 2015 in style, but there was no cause for party favors or confetti on his behalf after Thursday's affair. The defending champ struggled out the gate, suffering a cut over his left eye due to an accidental headbutt and struggling to slow down the attack of Argumedo, who was charged up for his first fight in 13 months. 

Takayama managed to turn the tide in round four, a momentum shift that carried over into a strong surge during the middle rounds. Argumedo appeared to have gassed, breathing heavily in between rounds and his punch output decreasing with each passing round. 

Something clicked in round eight, however, as the visiting challenger slugged his way back into the fight. Perhaps it was the sight of his opponent's blood, as Argumedo threw every remaining punch with knockout intentions. Takayama was summoned to visit the ringside physician on three separate occasions to have his left eye examined, including midway through round nine.

Mere moments after the last examination came another headbutt, this time producing a cut just outside Takayama's right eyelid. He braved the wounds and finished the round, but his corner decided that it was no longer in his best interest to continue. The decision came following another exam by the ringside doctor in between rounds, with Takayama slamming his fist along the top rope in frustration as the fight was stopped after nine rounds of action.

Confusion momentarily set in, as Argumedo was believed to have won by technical knockout. It was clarified soon thereafter that the fight ended due to cuts caused by an accidental foul rather than a punch, thus forcing the action to go to the scorecards. 

The clarification only delayed the eventual celebration by Argumedo, who lands by far the biggest win of his career as he improves to 16-3-1 (9KOs), 

As for Takayama, there's no telling what lies ahead in the future of an already unpredictable career. The 32-year old snaps a two-fight skid in watching yet another title reign cut short as he falls to 30-8 (12KOs). 

The bout aired live on TBS in Japan and TyC Sports both in the United States and Argentina.

Jake Donovan is the managing editor of Twitter: @JakeNDaBox