After years of fighting any middleweight who was willing, while stockpiling impressive streaks of knockouts and title defenses in the process, unified champion Gennady Golovkin enters a dangerous challenge against Daniel Jacobs. The pair of hard-punching middleweights will headline Saturday’s HBO PPV card (9 p.m. ET) from Madison Square Garden in New York, where Golovkin, a native of Kazakhstan, has built a boisterous following thanks to four knockout victories inside “The World’s Most Famous Arena.” Golovkin will look for his 24th consecutive knockout against Jacobs, a secondary titlist from the same Brownsville section of Brooklyn, New York, that has produced so many great fighters. Jacobs, who returned to boxing in 2012 after beating a rare form of bone cancer, is 10-0 with 10 KOs since coming back. GGG will also aim for his 18th straight title defense, which would move him two shy of Bernard Hopkins’ middleweight record.