The final chapter of Brian Viloria’s 18-year professional boxing career might be written in blood.

The 37-year-old from Waipahu failed in his bid for a fifth world title when he lost a unanimous decision to Artem Dalakian on the undercard of HBO’s Superfly 2 event on Saturday at The Forum in Inglewood, Calif.

Viloria (38-6, 23 KOs), who admitted before the fight it could be his last if he loses, suffered a nasty cut over his left eye in the 11th round from an illegal elbow.

The referee missed the illegal blow that had blood pouring down Viloria’s face for the final minutes of his 12-round fight for the vacant WBA flyweight title.

Dalakian (16-0, 11-0 KOs) won 118-109 on all three judges’ scorecards in his first fight in the United States.

The Star-Advertiser scored the fight 116-111 for Dalakian. Ring TV commentator Kevin Kelley had it 115-112.

Dalakian was deducted a point in the ninth round for repeatedly holding the back of Viloria’s head and pushing him to the ground. He first received a warning in the fourth round.

The blood that poured from Viloria’s forehead seemed to energize the Ukrainian, who dished out the majority of his punishment from that point on as Viloria faded.

Viloria, whose fight purse was $50,000, according to figures released by the California State Athletic Commission, dropped to 8-6 in his career in world title fights.

The only remaining active fighter from the 2000 Olympics, Viloria held the WBC junior flyweight title from 2005 to 2006 and won the IBF junior flyweight title in 2009.

He added the WBO flyweight belt to his résumé in 2011 with a victory over Julio Cesar Miranda in his final fight at the Blaisdell Arena, and knocked out Hernan Marquez for the WBA flyweight belt in 2012.