Referee Robert Byrd stopped the fight with 28 seconds left in the round.
Horn already has 2cm in height on Crawford and is expecting to be around 70kg by the time the bout begins.
"I just think businesswise it has to make sense", Crawford said. If he wants to fight three times a year or four times a year, we've got the dates for him. We knew how he was going to come.
"Like I told you all before, I'm strong. They seem to think I'm actually a lot mentally weaker than I am".
"I'm stronger than him". It may not be next on the docket, but it would be great for boxing to get those two in the ring together.
Crawford moved into a new weight category in the status of the absolute champion in the light Welterweight division.
LAS VEGAS - Terence "Bud" Crawford put the welterweight division on notice in a major way.
Crawford was a class above from start to finish, overwhelming Horn to hand the Australian a comprehensive defeat - his first in 20 professional fights - with a ninth-round technical knockout at the MGM Grand Garden Arena.
Horn, the former Brisbane schoolteacher who a year ago stunned Manny Pacquiao, initially weighed in just over the 147-pount threshold. He fought once since, stopping Gary Corcoran in Brisbane in December to retain his title. Crawford trapped him on the ropes, and with Horn unable to return fire, Byrd waved off the bout. The question of how well he can take punches at 147 against the likes of Errol Spence, JR. and Keith Thurman has yet to be answered though, as Horn is not renowned as a big puncher despite his size. Crawford's previous 10 opponents landed 7 per round.
"He was hard to tag, and he just kept me guessing", Horn said.
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He wants to be the Queenslander who took on world boxing's greatest mountain and conquered it.
The 30-year-old Crawford, of Omaha, Nebraska, and Horn, also 30, were supposed to fight April 14 at Mandalay Bay Events Center.
"When you're away from home, you have to win your rounds more clearly".
Horn is 30 and not likely to get much better - although he might get a bit smarter.
Welterweight has historically been boxing's glamour division, with the likes of Sugar Ray Robinson, Leonard, Mayweather, Thomas Hearns, Manny Pacquiao and others producing superfights such as Leonard-Hearns and Mayweather-Pacquiao.
In the second half of the battle horn exhausted, which allowed Crawford to finally make the fight one-sided. Such a fight would have no global cachet so perhaps Arum's stable is still his best bet.
Terence Crawford has a knack for making things look easy.
Though he never appeared frustrated, Horn couldn't find a rhythm against Crawford, who chuckled in the middle in the fourth, the same round he opened a small cut on Horn's left eyebrow.
The sixth round was as close to a winning round that Horn would see, but Crawford continued to serve a shutout by blocking punches and countering with stinging jabs to the face.
Crawford went on a rampage in the eighth round, rocking Horn with the last punch just before the bell but had to wait to finish the job. "That to me is a great, great compliment because I always thought Leonard was the best, and this guy is equal or better than Ray".