LAS VEGAS -- Erik Morales had been down just once previously in his career, and that was a questionable 12th-round knockdown in his first epic duel with Marco Antonio Barrera in 2000.
Then came the force known as Manny Pacquiao on Saturday night.
Pacquiao, seeking revenge for a unanimous decision loss to Morales last March 19, powered his way to a pair of knockdowns and a 10th-round TKO in a junior lightweight fight before a raucous crowd of 14,618 at the Thomas & Mack Center.
"I'm thankful to God for giving me great power, but with great power comes great responsibility," said Pacquiao, who pelted Morales with punches from all angles and gave him the worst beating of his career.
The huge contingent of Mexicans and Filipinos came to see an all-action fight between their national heroes and they got exactly that -- an early candidate for fight of the year.
But unlike the first fight, when Morales (48-4) had just enough to get past Pacquiao (41-3-2, 32 KOs), he couldn't do it this time. The years of vicious battles seemed to have finally taken their toll.
Morales' face was lumpy and bruised and he appeared out of gas as the 10th round started. Then Pacquiao finished him.
A left hand knocked Morales down to his knees. He clutched the ropes and alertly took an eight-count from referee Kenny Bayless before rising. But moments later, Pacquiao landed a pair of right hands that knocked Morales down again to his knees, and Bayless called it off at 2:33 without a count.
Morales was taken to Valley Hospital for observation.
"I could see he was having problems taking my punches," Pacquiao said. "I had no problem taking his. He never hurt me.
"I could take his power. I was able to land a lot more different punches this time. I saw that every time I hit him to the body he would stop punching, so
I knew he was hurt. I was still careful because he has great power."
"I was tired, and it was an accumulation of all the hard fights. But I was just tired," said Morales, in his first fight with new trainer Jose Lopez Sr. after dismissing his father, Jose Morales.
"I fell down because I was tired. I was tired because of making weight. The body can't take much more, and I was exhausted. It's hard to tell if I can make this weight (of 130 pounds) again. I am going to take a vacation. I'm just tired of boxing."
Pacquiao, allowed to wear his beloved Reyes brand gloves -- the "puncher's" glove -- said he felt more comfortable in this fight. In the first fight, Pacquiao was forced to wear the fluffier Winning gloves that Morales prefers, and he was not comfortable in them.
"The gloves helped a lot," Pacquiao said. "I like my gloves. The gloves were a big difference."
Pacquiao, who also owns a knockout win against Barrera, said his vision was better this time. In the first fight, Morales busted open a cut over Pacquiao's right eye in the fifth round and the blood dripping in his eye hindered his vision.
This time, Pacquiao didn't suffer any cuts.
"I could see the punches coming this time," he said. "I didn't have blood in my eye. I could see better."
HBO will replay the fight next Saturday night (9:45 ET) along with live coverage of Arturo Gatti vs. Thomas Damgaard.
Morales, a former three-division champion, has now lost three of his last four bouts -- his third fight to Barrera, a shocking upset decision loss to Zahir Raheem at lightweight last fall and now this knockout defeat.
With the series now 1-1, Morales' loss triggered an immediate rematch clause at his discretion. Pacquiao is up for it, and why shouldn't he be?
"If he wants a rematch, I will give him a rematch," Pacquiao said. "There should be a third fight."
Morales was doing well early in the fight, but Pacquiao trainer Freddie Roach believed "the tide turned in the sixth round."
"I could see Morales was fading from the body shots and Manny's right hook was beautiful," he said. "In the first fight, my guy was left hand happy. In this fight he landed a lot of right hooks. My guy got hurt a few times but he recovered quickly."
Morales, who earned at least $2.75 million, started strong and came close to scoring a first-round knockdown when Pacquiao, who made at least $2 million, was buckled by a punch and he nearly touched the canvas with his gloves.
Pacquiao staggered Morales in the second round with a left hand, sending him stumbling backwards and clutching the ropes to hold him up in what could have been ruled a knockdown.
Pacquiao began rocking Morales in the sixth, swarming him with rights and lefts as the Filipinos in the crowd began to chant "Manny! Manny!" It was a huge round for Pacquiao, who had a 32-8 advantage in power shots landed.
Morales nearly went down at the end of the round as he again grabbed the ropes to stay upright, but Bayless didn't call it.
By the eighth, Pacquiao was firmly in command, and in the ninth he was hurting a clearly tired Morales with every shot.
"He hit me with real good shots," Morales said. "I was getting hit a lot in the head. As the rounds went on, I was getting more tired. At the end I felt slow."
Dan Rafael is the boxing writer for ESPN.com.