NEW YORK – Xander Zayas took another significant step toward securing a junior middleweight world title shot Friday night.

The unbeaten Puerto Rican contender stopped previously unbeaten Slawa Spomer in the ninth round of their 10-round, 154-pound bout and maintained his No. 1 spot in the WBO’s rankings in The Theater at Madison Square Garden. Zayas’ left hook to Spomer’s body hurt him a few seconds after the midway mark of the ninth round.

An onslaught by Zayas (21-0, 13 KOs) made referee Charlie Fitch step between them and end their ESPN co-feature at 2:01 of the ninth round on the Denys Berinchyk-Keyshawn Davis undercard. Spomer never went down during their bout, which was among the reasons he questioned Fitch’s stoppage.

The 32-year-old Spomer, of Heilbronn, Germany, lost for the first time as a pro (20-1, 11 KOs). He is ranked 11th among the WBO’s contenders for junior middleweight champ Sebastian Fundora (21-1-1, 13 KOs).

A more active, accurate Zayas continued to pile up points during the eighth and ninth rounds, Once he landed the aforementioned body blow, though, Spomer couldn’t recover well enough to keep Fitch from stopping their bout.

Zayas boxed well during the sixth and seventh rounds. Spomer struggled to keep Zayas from coming forward in those six minutes, but Zayas didn’t hurt him with any of his head or body shots.

A second low blow by Zayas in as many rounds caused another break in the action with just under 30 seconds to go in the fifth round. Fitch again warned Zayas and gave Spomer some time to recover.

Zayas picked up the pace during the second half of the fourth round and put Spomer on his back foot by landing various power punches. Several seconds before the fourth round concluded, though, Spomer drilled Zayas with a right hand that made him move away from the action.

Spomer went down from a low left hook Zayas landed to his cup almost 30 seconds into the fourth round. Fitch admonished Zayas and gave Spomer time to recover after that foul.

Zayas and Spomer spent most of the third round trading short shots on the inside.

Spomer landed a left hook and his right hand in the opening minute of the second round. Zayas’ left hook temporarily stopped Spomer from coming forward after the halfway point of the second round.

Zayas landed a right hand that knocked Spomer backward during the final minute of the first round. Spomer began bleeding from his nose earlier in the opening round.