William Zepeda went more rounds than ever to lodge by far his best win to date.

A high-volume attack paved the way for the unbeaten Zepeda to surge past former IBF junior lightweight titlist Joseph ‘JoJo’ Diaz in a twelve-round, unanimous decision victory. Judges Carla Caiz (119-109), Zachary Young (119-109) and Fernando Villareal (118-110) all scored in favor of Zepeda in their DAZN-aired main event Saturday evening at Pechanga Arena in San Diego, California.

Diaz was prepared to take Zepeda’s best punches to make sure he was in position to land his power shots on the inside. The former titlist waded through the greater activity of his unbeaten and younger opponent to connect with his left hand and right hook to the body. Those moments came in between Zepeda’s cleaner punches upstairs, connecting with his straight left upstairs.

Action in round two was considerably more one way in favor of Zepeda. Diaz fought behind a high guard, picking off most of the incoming but also getting touched with Zepeda’s jab and left hand down the middle.

Zepeda forced Diaz to back into the ropes midway through round three. Diaz responded with a flurry of punches in the final minute, immediately met with a non-stop attack by Zepeda who tirelessly threw punches until the bell.

The same rate of activity by Zepeda carried into round four. The 26-year-old southpaw from San Mateo Atenco, Mexico began every combination with his right jab, landing left hands upstairs and never pardoning the body. Diaz was fighting bruising and swelling around his right eye, landing the occasional power shot but never able to keep the relentless Zepeda at bay or offset his high-volume attack.

Diaz’ corner banked on Zepeda eventually running out of gas but the opposite appeared to be the case. Zepeda didn’t show any signs of slowing down in round five, while Diaz was fighting with his mouth agape an only enjoying pockets of success.

A dramatic shift came early in round six, when Diaz landed a right hook immediately after eating a straight left hand. Zepeda briefly wobbled, but the moment was short-lived as Diaz failed to properly follow up on the sequence. Zepeda’s punch output decreased ever so slightly but still significantly outworked Diaz who came out of his shell to land a right hook and overhand left in the final ten seconds.

Zepeda continued to charge forward as the fight entered the second half. Even on the occasions where Diaz was landing the more telling blows, it came as Zepeda was more than tripling the volume of the former titlist.

Diaz cracked Zepeda with a right hook more than a minute into round nine. He threatened to follow up with a combination but was already beaten to the punch by Zepeda who was throwing in clips of eight and nine shots at a time.

Action understandably slowed in round ten. It provided Diaz with an opportunity to make something happen, letting his hands go with roughly 0:45 to go in the round. Zepeda took the shots well and immediately returned fire, with Diaz relying on his airtight defense to pick off most of the incoming attack.

The stellar chin of Diaz meant Zepeda was forced to see the eleventh round for the first time. It didn’t help turn the tide, though Zepeda spent the early portion of the frame fighting in bursts more than the constant swarm that came earlier in the fight. That changed in the final 80 seconds of the round, with Zepeda letting his hands go and physically forcing Diaz to the ropes.

With the fight seemingly well in the bag, Zepeda was cautioned by his corner to not discount one last surge from Diaz as the more experienced fighter. Diaz did his best to live up to that threat, throwing in combination and punching with Zepeda for the first time in the fight. Zepeda was unbothered by the adjustment, continuing to punch in bunches even as Diaz charged forward in the closing seconds of the fight.

Zepeda forges ahead to 27-0 (23KOs) with the win, his second straight to go to the scorecards after racking up fifteen consecutive knockouts. Diaz falls to 32-3-1 (15KOs), suffering his second straight defeat after dropping a twelve-round decision to Devin Haney (29-0, 15KOs) in their WBC lightweight title fight last December 4 in Las Vegas.

Jake Donovan is a senior writer for BoxingScene.com. Twitter: @JakeNDaBox