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EAST RUTHERFORD, N.J. -- Nate Diaz showed the value of his new black belt in jiu-jitsu by submitting one of the lightweight division's best grapplers on Saturday in the Ultimate Fighting Championship.

Diaz tapped out Jim Miller with a guillotine choke from top position in the second round of their main-event bout for UFC on Fox 3 in East Rutherford, N.J. The victory paves the way for Diaz to claim UFC's No. 1 contender slot in the lightweight division.

Miller tried to exchange strikes for much of the fight, but the taller, lankier Diaz, an outstanding brawler, often got the better of the smaller man.

"He had my number," Miller said afterward. "He just was landing strikes and hurting me."

By the second round, Diaz was engaging in his habitual goading of opponents, waving in Miller or casually dropping his hands and throwing a front kick. When Miller tried for a takedown, Diaz initially went for a one-armed guillotine choke before converting it into the winning choke after the fighters rolled over.

In Miller and Diaz, the fight paired Nos. 5 and 7 in the USA TODAY/SB Nation consensus rankings for lightweights. UFC promised Diaz a title shot with a win against Miller, although he could be shelved for many months if he waits for it, because champion Benson Henderson already has a rematch scheduled with ex-titleholder Frankie Edgar later this year.

Diaz was awarded a black belt in jiu-jitsu last month by his longtime coach, Cesar Gracie. Miller had never been submitted in a professional MMA fight until Saturday.

Fellow lightweight fighter Danny "Last Call" Castillo who trains in Sacramento with Urijah Faber's Team Alpha Malecontinued his recent run in the UFC, defeating Josh Cholish by a three round unanimous decision. The victory is Castillo's fourth in his last five fights in the UFC.