Gennady Golovkin earned a unanimous decision over Daniel Jacobs on Saturday to retain his middleweight belts but not before boxing's knockout king was taken the distance for the first time.
Golovkin was forced to go 12 rounds as Jacobs gave the middleweight superstar all he could handle in front of a boisterous crowd of 19,000 at Madison Square Garden.
Golovkin retained his WBC and WBO belts as two of boxing's pre-eminent punchers put on an entertaining show against the best opponents of their respective careers.
"I couldn't destroy him," said Golovkin. "He is a very clean, very good fighter. It is my first test for 12 rounds."
Judges Don Trella and Steve Weisfeld both scored the fight 115-112 and Max DeLuca had it 114-113 for Golovkin.
Cancer survivor Jacobs was an underdog going in but he used his 10-pound weight and reach to his advantage and possibly provided the blueprint for Canelo Alvarez to use against the 35-year-old Kazakh in a future title fight.
Golovkin, who improved to 37-0, floored Jacobs early in the fourth round with two rapid fire overhand rights to record the only knockdown of the fight.
Golovkin denied suggestions that he should have thrown more punches in the early rounds.
"This is sport. I am a boxer, I am not a killer. I respect his game," Golovkin said.
Golovkin had won 33 of his previous 36 fights by knockout as his 23 fight knockout streak, which dated back to 2008, came to a halt. He has a 92 percent knockout rate, the best ratio of any middleweight in boxing history.
Golovkin's IBF title was not on the line because Jacobs declined to attend the Saturday morning weigh in. Jacobs needed to be within 10 pounds of Friday's official weigh-in weight or lose the chance to fight for the IBF title.
The 30-year-old Jacobs decided the extra weight in the ring was more important than fighting for all of Golovkin's titles and the gamble almost paid off. He dropped to 32-2, with 29 knockouts.
"At times I stood toe-to-toe with him to see what the power was like, what everybody was talking about, and it wasn't that bad," Jacobs said.
Jacobs is nicknamed "Miracle Man" after his career was almost ended in 2011 because of osteosarcoma, a rare form of bone cancer. He made a full recovery but spent 19 months out of the sport while battling and recovering from cancer.
Jacobs felt he won the fight but said the judge's favoured the champion.
"Daniel Jacobs got X-ed out," he said. "I won the fight by at least two rounds."
On the undercard, Thailand's Srisaket Sor Rungvisai captured the WBC super flyweight title with a stunning majority decision over unbeaten champion Roman Gonzalez.
The former star Muay Thai fighter, who once worked as garbage man to help finance his early boxing career, continued his amazing victory run by handing Gonzalez the first loss of his career.
Srisaket has now won 41 or his last 42 fights as he improves to 42-4 overall with one drawn and 38 knockouts.
"He is one of the best fighters but the reason I won is because I have all the help and encouragement from the people of Thailand," Srisaket said.
Nicaragua's Gonzalez, who goes by the nickname "Chocolatito", is considered one of the best pound-for-pound fighters in the world and was a heavy favourite going into the 12-round fight.
He suffered a couple of cuts over his right eye which bleed profusely throughout much of the fight and hampered his vision.
Gonzalez, who dropped to 46-1, immediately left the ring without making any comments.
Former WBC champion Srisaket's only loss since 2010 came three years ago when he fell to Mexico's Carlos Cuadras.
In the final round, the worn-out Thai southpaw was booed because he spent much of it either running away or clutching and grabbing Gonzalez in the centre of the ring.
Gonzalez, in his 16th world title fight, became a world champion in his fourth weight division in September by taking a unanimous decision victory over Cuadras.
Gonzalez lost Saturday's fight despite landing 441 punches compared to just 284 punches landed for Srisaket.