Jaron “Boots” Ennis navigated the deepest waters of his professional career before stopping Xander Zayas on Saturday night in a wildly entertaining scrap to capture the WBA and WBO super-welterweight titles and become a two-division world champion.

The unbeaten Ennis knocked Zayas down three times and fought through a heart-stopping third-round crisis before referee Harvey Dock halted the bout at 1:49 of the seventh round in front of an announced sellout crowd at Barclays Center, giving the Philadelphia native the signature victory that had eluded him despite years of being regarded as one of boxing’s brightest talents.

Ennis improved to 36-0 with 32 knockouts, while Zayas suffered the first defeat of his career after entering the fight 23-0.

“I put on a show for the fans and I appreciated [Zayas] taking this, because he didn’t have to,” said Ennis, who turned 29 on Friday. “I feel tremendous hearing ‘and the new unified world champion at 154.’”

The bout had been billed as one of the year’s most compelling matchups, pairing two unbeaten champions who had been touted as future stars since their teenage years. It quickly lived up to expectations.

Ennis took control from the first bell, seizing the center of the ring and repeatedly beating Zayas to the punch with a stiff, spearing jab. Late in the opening round he dropped the Puerto Rican with a straight left that capped a blistering combination, sending much of the crowd to its feet.

Zayas beat the count but looked shaken returning to his corner after absorbing several clean power shots.

Ennis continued to press the action in the second, switching comfortably between orthodox and southpaw stances while repeatedly finding openings through Zayas’s guard. The younger champion struggled to match Ennis’s hand speed as the favorite appeared on course for a relatively straightforward night.

Instead, the fight caught fire in the third. Zayas landed a flush right hand through Ennis’s guard that rocked the challenger and backed him toward the ropes, forcing him to clinch as Barclays Center erupted. Ennis, hurt more seriously than at perhaps any point in his professional career, fired back while retreating as both fighters traded concussive blows through the closing seconds of a frenetic round.

The breathless two-way action carried into the fourth, with Zayas enjoying his best spell of the fight by finding success with his jab and body attack while Ennis answered with crisp flurries of his own in increasingly violent exchanges.

The turning point came in the fifth. Ennis seized control for good when he dropped Zayas for a second time with a perfectly timed right uppercut. Zayas barely rose at the count of nine and survived the round, but the knockdown shifted the momentum back toward the former unified 147lb champion.

After a comparatively quieter sixth round, Ennis closed the show in the seventh. He trapped Zayas against the ropes with a series of spiteful right hands and left hooks before sending him to a knee for a third knockdown. The referee made it to a count of five before waving it off just as Zayas’s corner threw in the towel.

“I knew he would come forward, and we were ready for it,” Ennis said. “I just took my time, stayed patient, and listened to my corner.”

The victory gives Ennis two of the major world titles at 154lb and strengthens his position in one of boxing’s deepest divisions after moving up from welterweight last year. He had previously held the WBA’s interim title at super-welterweight after blasting through the overmatched Uisma Lima in a single round last year in his first outing at the weight.

Attention is now likely to turn back to fellow unbeaten Vergil Ortiz Jr. A bout between the two appeared close earlier this year before Ortiz’s contractual dispute with Golden Boy Promotions derailed negotiations. Saturday’s result is likely to renew calls for one of the biggest fights that can be made at 154lb. It will also bolster Ennis’s case for a place near the top of boxing’s pound-for-pound rankings after years in which his talent often outstripped his résumé.

“Give me Vergil, or bring on them belts, it doesn’t matter who it is,” he said. “I’m taking over this division. This weight division is mine.”

For Zayas, the defeat halted an unbeaten run that began when he turned professional as a teenager. The 23-year-old had unified the WBA and WBO titles after becoming boxing’s youngest active world champion last summer and has widely been put forth as Puerto Rico’s next boxing star in the lineage of Wilfredo Benítez, Héctor Camacho, Félix Trinidad and Miguel Cotto.

“It’s part of the business,” said Zayas, who was transported by ambulance to a local hospital for precautionary evaluation after the fight and did not attend the post-fight news conference. “You live, you learn, you come back again.”

He added: “I’m happy with my performance. It was not what I was expecting, not what I trained for, but I knew I had one of the best in front of me. ... He hurt me in the first round and my legs went away for a couple of rounds. ... Then I hurt him, but he got me again. You learn and you come back and get better.”

Saturday’s bout represented the first elite test for both fighters. Ennis had spent years searching for marquee opponents before moving to 154lb, while Zayas elected to face the toughest challenge of his career rather than continue a more gradual rise through the division.

“He’s a grown man,” Ennis said of the fallen champion. “He’s durable. He’s a big guy. I knew he was going to be able to take some punches. ... I had respect for him. He didn’t have to take this fight, he could have faced somebody else. But he wanted to test himself against one of the best, and I commend him on that.”