WBA middleweight beltholder Gennady Golovkin extended his unbeaten record and increased his awesome KO ratio with a one-punch (body shot) knockout of top-10 contender and former title challenger Matthew Macklin on Saturday in Mashantucket, Conn.

Golovkin (28-0, 24 knockouts) was in command from the opening bell, stalking the battle-tested Englishman with a hard jab to the ropes where he dished out power shots and body punches. A left hook delivered to the liver with Macklin (29-5, 20 KOs) against the ropes abruptly ended the HBO Boxing After Dark main event.

Macklin, who lasted into the 11th round with RING champ Sergio Martinez and lost a dubious decision to then-WBA titleholder Felix Sturm, was down for the count and remained on the canvas long after referee Eddie Cotton waved the bout off at 1:22 of the round.

“Without a shadow of a doubt he’s the best I’ve fought,” Macklin said of Golovkin. “He was patient, he was hard to hit clean. Every shot is hard, even his jab. I was so preoccupied with the punches upstairs that he got me downstairs.”

A full ringside report by Tim Smith will be posted soon.