Kazakhstan's Zhanat Zhakiyanov survived two first-round knockdowns to upset Rau'shee Warren by split decision on Friday and claim the World Boxing Association bantamweight world title.
On the same card in Toledo, Ohio, unbeaten Robert Easter retained his International Boxing Federation lightweight title with a unanimous decision over Puerto Rico's Luis Cruz.
Warren, making his first defense of the title he claimed with a majority decision win over Juan Carlos Payano, looked headed for a short night when he put the challenger down twice in the first three minutes.
But Zhakiyanov, trained by Britain's former two-division world champion Ricky Hatton, steadied and gradually seized control of the bout.
He hurt Warren with a pair of right hands in the third round and Warren was on the canvas moments later, although referee Gary Rosato ruled he'd been pushed rather than knocked down.
For the rest of the fight Zhakiyanov attacked relentlessly, his punishing body blows particularly effective against the American southpaw.
While one judge saw it 115-111 for Warren, Zhakiyanov got the nod from the other two by scores of 116-110 and 115-111.
Zhakiyanov, 33, was fighting for the first time since a split decision victory over Yonfrez Parejo in Monte Carlo in November of 2015. He improved to 27-1 with 18 knockouts while Warren fell to 14-2.
Easter, a Toledo native, knocked down Cruz three times -- in the 10th, 11th and 12th rounds -- en route to victory.
He won by scores of 119-106, 118-107 and 117-108 to improve to 19-0 with 14 knockouts, while Cruz fell to 22-5 with one drawn.