LAS VEGAS - Bernard Hopkins told everyone who would listen that he had a foolproof plan for getting inside Winky Wright’s impenetrable defense.

Hopkins claims that plan didn’t include a timely head-butt. Still, it turned out to be the decisive blow in the latest remarkable chapter of Hopkins’ career.

The 42-year-old Hopkins earned another stunning victory in the twilight of his fighting days Saturday night, ending Wright’s 7½-year unbeaten streak with a unanimous decision in their 170-pound matchup at the Mandalay Bay Events Center.

Hopkins (48-4-1, 32 KOs) landed his biggest blow when he opened a gash over Wright’s left eye with a head-butt in the third round. Hopkins spent the night picking at it while Wright (51-4-1) scrambled and counterpunched, his face showing frustration and fatigue as the fight slipped away.

“You put the bait out there, the fish gets a little closer, and then you pull the bait back,” Hopkins said, calling it a “bait-and-switch” plan.

It worked, and Wright was sunk.

“It was a tough fight, a very close fight,” Hopkins said. “Winky is tough, and he kept coming. He knows that I respect him a lot. I had no ill intent. It was all good for both gentlemen, and boxing is back.”

Hopkins retired last year after a career highlighted by 21 straight middleweight title defenses and last year’s shocking win over Antonio Tarver. Months later, he abandoned retirement for a shot at the 35-year-old Wright, who hadn’t lost in 13 fights since December 1999.

Wright grew frustrated and tired in the late rounds, and Hopkins stuck with his patient, steady strategy in a light-heavyweight fight featuring more action than most expected from two defensive masters. Wright was active and resilient, but Hopkins usually was a half-step ahead.

Judges Glenn Trowbridge and Dave Moretti scored it 117-111 for Hopkins, and Glenn Hamada scored it 116-112. The Associated Press also gave it to Hopkins, 115-113.

The punch statistics were nearly as even as the fight. Hopkins landed 152 of his 640 punches, and Wright landed 167 of his 618 blows.

The night started tough and got worse for Wright, who didn’t appear comfortable at the heaviest weight of his career. His corner profanely ridiculed the decision while Hopkins celebrated.

“I won the fight,” said Wright, who doesn’t plan to fight again at 170 pounds. “It was a dirty fight. He was head-butting all day. I still want to fight the best. I thought I won the fight, but it was a close fight. ... I don’t think the head butt was intentional. It was a head-butt. That’s that.”

Though the fight matched two veterans known best for their defense and counterpunching, a potentially boring matchup got interesting at Friday’s weigh-in. After the fighters exchanged insults, Hopkins shoved Wright in the face, precipitating a brief scuffle between their entourages. Hopkins could face a hefty fine because of his actions.

After gaining 10 pounds of muscle for his first fight as a light heavyweight, Wright wasn’t the defensive fighter who has never been knocked out. He charged Hopkins and forced early action — but early in the third, the fighters bumped heads while Wright moved forward, opening a gash over Wright’s left eye.

Wright gestured angrily at Hopkins, apparently feeling the bump was on purpose — though he changed his mind afterward.

“He was coming towards me, and I was going under,” Hopkins said. “It definitely was an accidental head-butt. It happens a lot when you fight southpaws.”

Hopkins’ legacy already is secure after his record 21 straight defenses of his middleweight title, and he already left boxing on a perfect note last year with a remarkable upset victory over Tarver — but couldn’t resist the lure of the ring.

He originally hoped to fight as a heavyweight before accepting a match with Wright, who had Hopkins near the top of his “hit list” of potential opponents.

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Critics and many fans derided Hopkins’ matchup with Wright from the moment it was announced because it matched two cautious fighters. Wright hadn’t knocked out an opponent since 2002, while Hopkins had just one knockout in the same stretch against Oscar De La Hoya.

But Wright hadn’t lost in 7½ years, with only a disputed draw against Jermain Taylor blemishing his record. After a career spent chasing good fights against contenders who didn’t want to risk facing his left-handed style, Wright has made up for lost time with a series of strong outings that began with two victories over Sugar Shane Mosley in 2004.

Hopkins also lost his previous two fights to Taylor before upsetting Tarver, leading many to think the courageous ex-convict’s best days were behind him.

“I want Joe Calzaghe next,” Hopkins said of the Welsh 168-pound champion. “Tell him to come over here, and I’m going to beat him, too.”