Conor McGregor puts up and doesn’t shut up after beating Chad Mendes

Conor McGregor wouldn’t keep quiet, not by punches to the mouth, extended punishment with his back on the canvas or a near chokehold.

So, in the end, in a compelling second-round stoppage of the Ultimate Fighting Championship’s top-ranked featherweight contender Chad Mendes on Saturday night at MGM Grand, the boisterous Irishman let rip a jaw-crushing left-handed punch that makes McGregor the UFC’s interim 145-pound champion.

“I could go all … day,” McGregor roared to a sellout UFC 189 crowd packed with thousands of fans from his home country waving Irish flags. “I’m blown away by the support.”

After dropping Sacramento’s Mendes (17-3) with the devastating left, McGregor (18-2) delivered four more right-handed punches to Mendes’ head before referee Herb Dean stopped the bout with three seconds remaining in the second.

“I’ve been hearing all this about being protected and gifted a title shot,” McGregor told the crowd in the octagon afterward. “It doesn’t matter who it is” as the opponent.

And after that outcome, McGregor’s originally planned title shot at Brazilian champion Jose Aldo becomes all the more richer. Aldo withdrew from the bout last month after suffering a rib injury in training.

“I’ve had bigger injuries than that bruised rib for this fight,” McGregor said. “He can come back, but I swear to God, his days are numbered.”

McGregor’s major accomplishment Saturday was proving his colorful talk and fight hype were backed by championship skill.

His previous claims appeared suspect considering the quality of recent competition, but while fighting Mendes, who has lost two title shots at Aldo, McGregor met his proving ground.

A polished wrestler, Mendes answered McGregor’s early left hands with a first-round takedown and some ensuing punishment on the ground. McGregor was cut near the right eye.

McGregor rose, hit Mendes with a good left, then escaped a choke attempt near the end of the first.

Mendes wanted more ground and pound in the second, and referee Dean let him have it after an early takedown. A right elbow, fist and forearm rocked McGregor, as he appeared to plead with Dean to get the fight back to striking.

When Mendes failed to hold another choke attempt, McGregor got up, sent Mendes a twisted, menacing look and started swinging. He dazed Mendes with four lefts that backed him toward the cage. A jab set up the defining punch.

“The guy talks,” Mendes said. “But he’s got the stuff to back it up.”

In the earlier welterweight title fight, champion Robbie Lawler scored a fifth-round technical knockout of his younger Canadian challenger Rory MacDonald.

Lawler turned things in his favor by landing a vicious right-left combination of punches to the nose in the first round.

The southpaw champion proceeded to repeatedly land clean lefts to MacDonald’s nose, leaving the challenger a bloody mess before ending the bout with a crushing left to the nose that forced MacDonald to crumple to the canvas, victory recorded one minute into the fifth round.

“That was the accumulation of a beatdown,” Lawler said. “I’m a true fighter. I come to fight.”

In his first title defense, Lawler, 33, of Florida, withstood a MacDonald rally in the third round that caused the champion to wobble after a right kick and punch to the head. MacDonald (18-3) split Lawler’s lip in the ensuing assault.

“I was dinged,” Lawler admitted after spitting out his own blood at the end of the round with MacDonald watching. “But I keep fighting.”

Lawler answered MacDonald’s early pressure in the fourth with more deliberate, precise punches. In 2013, Lawler beat MacDonald by a split decision.

“My coach told me to stay basic, that I’d pick him apart and knock him out,” said Lawler (26-10).

lance.pugmire@latimes.com

Twitter: @latimespugmire