Unified world heavyweight champion Andy Ruiz Jr has claimed Anthony Joshua is "not good at boxing" and vowed to land another victory when they fight again.
Ruiz, 29, stunned Joshua to win the IBF, WBA and WBO titles on 1 June and is under contract to take a rematch.
The rematch has been mooted for later this year, with a return to New York's Madison Square Garden a possibility.
"The rematch is going to be the same. I am going to be more prepared and more ready," Ruiz said.
"I know his flaws. I can do a lot better. The only thing that he can do is just run around, he's not good at boxing."
'I bought mum a car'
Ruiz was born in California but fights under a Mexican flag by virtue of his parents' nationality, and consequently became Mexico's first-ever world heavyweight champion.
On Saturday he returned to Imperial, California, and - flanked by a Mexican Mariachi band - was paraded through the area where he grew up in the back of a convertible car.
It capped a "rollercoaster" three weeks since he floored Joshua four times to inflict a seventh-round stoppage and a first career defeat on a man who was a 1-25 favourite with bookmakers.
Ruiz was a late replacement to face the Briton, and since the win has appeared on high-profile US talk shows, shown off his titles in Mexico City and seen his Instagram following rocket from 60,000 to 960,000.
He earned a reported $7m (£5.5m) for the bout. On Saturday, he told reporters: "First of all I bought a car for my mum, that was the first purchase I made from the money I got. I messed up a lot of her cars when I was young so I got her a brand new car."
Joshua's promoter Eddie Hearn has said his fighter seems keen to return to Madison Square Garden to avenge the defeat, which came on his much publicised US debut.
Ruiz - who was at times ridiculed for his rotund physique in fight week - vowed to weigh in lighter than the 268lbs he scaled before their original bout.
"People thought I wasn't going to do anything, I was too big, too overweight," he added. "I don't want to say all the things I am going to change.
"There is going to be a lot of changing, I am going to come at a better weight this time. It's going to be a hell of a fight."