Daniel Jacobs smiled in his corner after an action-packed third round, looking pleased to be in a tough fight.
It wasn't clear he would win it until he knocked Maciej Sulecki down with the kind of punch he wants to throw at the middleweight division's biggest names.
The 12th-round knockdown helped Jacobs win a unanimous decision Saturday night, strengthening his hopes of getting another title shot.
Jacobs pulled out a competitive fight, winning by scores of 117-110, 116-111 and 115-112 and handing the Polish fighter his first loss.
Jacobs (34-2-0) became the mandatory challenger for the WBA 160-pound title, giving the popular Brooklyn fighter and cancer survivor hopes of a chance to avenge his loss to Gennady Golovkin from last year.
Jacobs had a much tougher time with Sulecki (26-1), who seemed to gain confidence as the fight went on and was getting the better of some of the action in the late rounds until Jacobs caught him with a quick right to the head early in the 12th, sending Sulecki to the canvas as Brooklyn fans roared for the hometown fighter.
There had been chants of "Brook-lyn, Brook-lyn" earlier in the bout from the local fans that made up the announced crowd of 7,892 at Barclays Center. But the vocal section of Polish fans grew louder in the later rounds as their fighter rallied.