ANAHEIM, Calif. — Cain Velasquez stopped Brock Lesnar late in the first round with a relentless flurry of punches, claiming Lesnar's UFC heavyweight title at UFC 121 on Saturday.

ANAHEIM, Calif. — Cain Velasquez stopped Brock Lesnar late in the first round with a relentless flurry of punches, claiming Lesnar's UFC heavyweight title at UFC 121 on Saturday.

Velasquez (9-0) remained unbeaten by outpunching the fearsome Lesnar, the UFC's biggest star and top pay-per-view draw. After a frenetic opening minute featuring huge blows by both fighters, Velasquez relentlessly pursued the bigger champion and eventually staggered him across the ring.

Lesnar (5-2) tried to cover up near the cage, but Velasquez mercilessly rained down blows on Lesnar and eventually broke his guard, forcing referee Herb Dean to stop the fight.

Lesnar's third title defense came just four months after his return to the octagon following a yearlong bout with diverticulitis, an intestinal malady that threatened his life and forced him to revamp his training and diet. The former professional wrestler and football player adapted without losing the sheer bulk that makes him the toughest physical matchup in the UFC.

But he had never faced a fighter with the athleticism and well-rounded skills of Velasquez, the former Arizona State wrestler who trains at a famed kickboxing academy in San Jose. Velasquez also drew motivation from the chance to become the first Mexican-American heavyweight champion in a major promotion in either MMA or boxing.

Jake Shields also won a contentious split decision over Martin Kampmann in his UFC debut, extending his career winning streak to 15 fights. Matt Hamill beat Tito Ortiz by unanimous decision to keep the former light heavyweight champion winless in the past four years, and Diego Sanchez beat Paulo Thiago by unanimous decision at Honda Center.