At Diaz met the heavy-handed former UFC veteran Scott Smith at a Catchweight of 180 pounds. Although Smith took Diaz down once in the first round, Diaz controlled the majority of the bout with his superior boxing, utilizing his reach, stalking jabs and repeatedly punishing Smith with hooks to the body, twice dropping him in the second and third round. Upon landing the body shot that dropped Smith in the third round, Smith assumed a "turtle" position and Diaz took his back until securing a rear-naked choke to finish the bout at 1:41 of the final round.