LAS VEGAS – As things turned out, it was over before it started.

For eight long rounds Saturday night, Manny Pacquiao beat the bejesus out of someone claiming to be Oscar De La Hoya. The guy looked like De La Hoya, at least until about the sixth round, but he didn’t fight like him. He fought like Oscar Madison.

From the opening bell until trainer Nacho Beristain nodded to referee Tony Weeks after a particularly one-sided eighth round and stopped the fight with De La Hoya sitting on his stool, his left eye half closed and badly bruised and all the fight long beaten out of him, there was only one fighter in the ring at the MGM Grand Garden Arena.

One fighter punching holes in a shadow of what De La Hoya once had been. One man at the height of his powers, fast, elusive, accurate and supremely confident, and another who was old, slow and without a single answer to the problems he was facing.

Although much of the pre-fight talk had been about the size difference between De La Hoya and Pacquiao, the story was speed. Pacquiao had it and De La Hoya did not.

Pacquiao’s trainer, Freddie Roach, had promised as much months ago and it was evident from the first round, when De La Hoya seemed hesitant and unwilling to release what had once been a dominant jab that this would be a long night for an old man.

“After the first round I knew he had no legs,’’ Roach said of De La Hoya. “He was shot.’’

He was also taking shots, primarily big straight left hands that kept slamming into his face as if someone was covering his eyes. Pacquiao’s quick left time after time shot between the small openings between De La Hoya’s gloves and smacked him flush.

Seldom did De La Hoya (39-6, 30 KO) even attempt to mount an offensive, so concerned was he with the puzzle he could not solve. He was repeatedly hit with fast combinations and as the rounds went by Pacquiao moved closer and closer and scored more and more, yet always seeming to get back out of range before De La Hoya could react.

“I knew right away I could win,’’ Pacquiao said. “I controlled the fight. I was able to defend his jab and move.’’

What would prove to very likely the final round of De La Hoya’s career was a three-minute beating in Round 8. Time after time Pacquiao struck De La Hoya with the straight left, a punch the six-time world champion could no longer see coming because his left eye was half closed and badly discolored.

Three times Pacquiao drove him back into the ropes and strafed him with punches from forehead to chin with not the hint of anything coming back as Weeks watched closely. When that round ended, De La Hoya walked slowly back to his corner and slumped on his stool. At that point they could have changed the name of his company from Golden Boy Promotions to Swollen Boy Promotions because that’s what he was, except that he clearly was a boy no longer. He was an old man in the wrong neighborhood after dark.

“My style is to go forward but he was back on his toes all night waiting for me to make my mistakes,’’ De La Hoya said. “He was a better man tonight.’’

Pacquiao (48-3-2, 36 KO) sensed that almost immediately, seeing that De La Hoya had no answer for the speed with which he was tearing him to shreads, bit by bit. Things grew so one sided that the three judges not only gave every round to Pacquiao but also scored the seventh round 10-8. That was deserved despite the fact there was no knockdown but frankly Round 8 was even worse.

It was no way to end what had been a brilliant career but there was also no point in continuing and so Beristain told Weeks his fighter had had enough.

“I didn’t want him to leave his greatness in the ring,’’ Beristain said later.

By then it was so one-sided that even De La Hoya willingly conceded the point, walking over to Roach, who had insisted throughout the promotion that De La Hoya could no longer pull the trigger, and agreed with him.

“You’re right Freddie,’’ De La Hoya said. “I don’t have it any more.’’

Pacquiao’s speed advantage was clear through the fight as he repeatedly landed a straight left hand to the face that De La Hoya seemed confounded by and unable to avoid. Pacquiao was not only landing but also getting in and out so fast De La Hoya was troubled as to how to respond and by the time he did Pacquiao was seldom close enough to be touched by him.

The De La Hoya jab was never in evidence and the few times he tried to throw it the punch lacked snap. He looked like someone who had simply fought one fight too long and paid a heavy price for it all night long.

De La Hoya’s face had begun to flush red and swelling had formed around his eyes from the straight left hands Pacquiao kept catching him with by the fourth round and that condition only worsened. As Roach had promised size was not the deciding factor. Speed was and De La Hoya seemed to have little of it left.

The beginning of the end came midway through round 7 when Pacquiao climbed all over De La Hoya, backing him into his own corner and battering his left eye half shut with an unanswered string of rights and lefts. He wobbled De La Hoya with one stinging left that buckled him momentarily. He steadied himself but had no response except to steadfastly stand and take a beating until Beristain stepped in. By the time he did the fight itself had long been decided and frankly so had the future of Oscar De La Hoya.

In a boxing ring at least, he had none.