NEW YORK: 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. Photo by Tom Hogan/Hoganphotos.

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.

While Jacobs did go down in the fourth round, Golovkin and his handlers realized that the Brooklyn fighter was not really hurt from the two big punches that connected.

"Gennady dropped him, but you could tell Danny wasn't hurt from the punch,"said Golovkin's promoter Tom Loeffler of K2 Promotions.

Golovkin retained his WBC, IBO and WBA 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.

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.