American Ryan Garcia floored Devin Haney three times in a majority points win over his compatriot on a dramatic night in Brooklyn, New York.
Garcia’s left hook was his greatest asset as the previously unbeaten world champion Haney was floored in the seventh, 10th and 11th rounds.
Scorecards of 112-112, 114-110 and 115-109 saw the decision go to Garcia.
The Californian, however, did not win Haney’s WBC light-welterweight title after missing weight for the contest.
“You really thought I was crazy? You all lost your own minds,” said Garcia, who had been criticised for his behaviour in the build-up.
The 25-year-old had posted a series of erratic, often unsubstantiated and defamatory social media posts in recent months.
“You guys overegg everything,” Garcia added.
He extended his record to 25 wins and one defeat, while it was Haney’s first pro defeat in 32 bouts.
In his post-fight news conference, Garcia said he had been “drinking every night” in the build-up to the bout after getting divorced earlier this year.
“Not necessarily am I proud of that, but I’m just saying – I do whatever I want and still win,” he added.
A marked-up Haney, 25, said he was “disappointed” in his performance.
He added: “I [showed I] was a true champion and I could fight after being knocked down.”
On the undercard, Belfast’s Sean McComb was controversially defeated by light-welterweight Arnold Barboza Jr.
