By Keith Idec

LAS VEGAS – This time, Canelo Alvarez really wasn’t f***ing around.

Alvarez announced immediately after his 12-round beatdown of Julio Cesar Chavez Jr. on Saturday night that he’ll finally fight Gennady Golovkin in his next bout. The unbeaten Golovkin was ushered into the ring amid loud entrance music and Alvarez announced that they have an agreement in place to fight September 16 in an HBO Pay-Per-View main event.

“Yes, sir,” Alvarez told HBO’s Max Kellerman in the ring early Sunday morning. “It’s done. It’s done.”

The site of the Alvarez-Golovkin fight wasn’t announced.

The announcement of the long-awaited showdown was made in the same T-Mobile Arena ring where Alvarez promised Golovkin (37-0, 33 KOs) almost a year ago to the day that he would fight him last September.

During that animated rant following his sixth-round knockout of Amir Khan, Alvarez said, “Mexicans don’t f*** around.” Despite that tough talk, Alvarez (49-1-1, 34 KOs) fought two other opponents before finally agreeing to challenge Golovkin for his middleweight titles.

Instead of facing Golovkin last September, Alvarez knocked out Liam Smith in the ninth round to win the WBO super welterweight title September 17 in Arlington, Texas. The Mexican superstar then opted to fight Chavez on Saturday night, which sparked speculation that Alvarez would continue to avoid the knockout artist from Kazakhstan.

The 26-year-old Alvarez apparently had heard enough criticism from fans, particularly in Mexico, and decided that he has to fight Golovkin next. It probably didn’t hurt that Golovkin looked human in his last fight, in which Daniel Jacobs ended Golovkin’s 23-fight winning streak and nearly upset him March 18 at Madison Square Garden.

“I’m very exicted,” Golovkin said. “In September, I will bring the Mexican style. Big drama show. … Congrats to Canelo [on beating Chavez]. He looked good. I think everyone is excited.”

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.