No fighter had ever submitted Miller in a mixed martial arts contest. And few people expected Diaz to pull off the feat.
But Diaz hurt Miller with his patented left-right combinations in the second round. He also landed several knees to the chin that wobbled Miller.
Diaz eventually got Miller on the mat where he was able to apply a guillotine choke. Miller was forced to tap for the first time in his career at the 4:09 mark.
"I know [Miller's] a great fighter," Diaz said after improving to 15-7. "I have nothing bad to say about him."
The victory put Diaz atop the lightweight contender list.
"He had my number," Miller said. "Nate's a tough guy. I knew he was tough coming in. He deserves that shot."
Miller falls to 21-4.
Hendricks sneaks past Miller
Two judges scored the fight 29-28 for Hendricks, who delivered several hard left hands that caused swelling around Koscheck's right eye.
The third judge had Koscheck winning 29-28. ESPN.com also had Koscheck winning 29-28.
Though Koscheck is disappointed with the loss, the greater concern might be the status of his right eye. The swelling is in the same area where Koscheck suffered a broken orbital bone after a title loss to 170-pound champion Georges St. Pierre in December 2010.
That injury sidelined Koscheck for 10 months.
"That's one tough dude," Hendricks said of Koscheck. "I hit him with everything I've got.
"I knew he was going to be one tough fighter."
UFC president Dana White said before the bout that a win by Hendricks would put him in position to fight for the title.
St. Pierre is slated to defend his belt against interim titleholder Carlos Condit later this year.
Belcher takes down ground-specialist Palhares
That is exactly what Belcher opted to do, avoiding Palhares' submission attempts and pounding out a first-round TKO.
Belcher delivered elbows and punches that forced Palhares to cover up. When Palhares failed to fight back, referee Dan Miragliotta waved the fight off at the 4:18 mark.
"I wasn't scared in this fight," Belcher said. "I wanted to prove I could beat the toughest man on the ground. I'm coming for that belt."
Johnson finishes Barry in first round
Pat Barry and Lavar Johnson aren't well-rounded mixed martial artists, but each can finish a fight with punches.
Neither man was shy in saying their heavyweight bout would not last long. And it didn't.
Johnson landed several right uppercuts that wore Barry down. Then he connected with an overhand left that sent Barry to the canvas at 4:38 of the first round.
Barry never returned to his feet, allowing Johnson to register his second consecutive win via TKO.
Johnson's movement, left hand neutralizes Ferguson
Johnson, who replaced Thiago Tavares, never let the hard-hitting Ferguson find a rhythm. He moved constantly throughout the fight, slipping punches and catching kicks.
Each time one of Ferguson's kicks was caught, Johnson countered with a left hand.
With the win, Johnson improves to 11-6. He has won two fights in a row.
Ferguson, who won Season 14 of TUF, suffers his first setback inside the Octagon. He is 13-3.
John Dodson injured his left hand in the second round of a flyweight bout with Tim Elliott, but held on to earn a unanimous decision.
Each judge scored the fight 29-28 for Dodson. ESPN.com also gave the advantage to Dodson, 29-28.
"The Ultimate Fighter" winner landed hard punches and knees in the first two rounds to take a 20-18 edge into the third.
Knowing he was trailing in the fight, Elliott picked up his aggression, connecting with several right hands and some knees.
But it wasn't enough to pull off the comeback.
Hathaway overwhelms Krauss for decision
Welterweight John Hathaway returned to action for the first time in more than a year with an impressive unanimous decision over Pascal Krauss.
The judges favored Hathaway by scores of 29-28, 30-27 and 30-27. ESPN.com had Hathaway winning 30-27.
Hathaway quickly found his rhythm with a left knee that dropped Krauss in the opening round. On the mat, Hathaway landed several punches.
Throughout the rest of the fight, Hathaway dominated in a standing position, but also took Krauss to the mat on a few occasions.
It was Hathaway's first appearance in the Octagon since March 26, 2011, when he beat Kris McCray by unanimous decision.
Gaudinot submits hard-hitting Lineker
In a 127-pound catchweight fight dominated by strikes, Louis Gaudinot finished John Lineker with a guillotine in the second round.
The bout was originally slated for a non-title 126-pound flyweight battle, but Lineker came in one pound over. New Jersey State Athletic Control Board physicians, however, refused to let him drop any more weight.
Lineker won the standup battle with hard right hands to the body. The left side of Gaudinot's body was red from all the shots he took there.
But Gaudinot was able to take Lineker down in the second and apply a guillotine. Lineker lost consciousness at 4:54 of the round.
Castillo ends Cholish's win streak at 8
Danny Castillo was able to slam John Cholish several times in their lightweight bout to earn a unanimous decision.
All three judges scored the fight 30-27. ESPN.com had Castillo winning 29-28.
Each fighter possesses solid wrestling skills, so striking played a huge part in their fight plan. Cholish landed several left jabs, but none did any damage.
Castillo improves to 14-4 with his third straight win.
After winning eight in a row, Cholish loses for the second time as a pro.
Bermudez snaps skid by taking down Garza
Dennis Bermudez snapped a three-fight skid with a dominating unanimous decision over Pablo Garza.
All three judges scored the fight 30-27. ESPN.com also had Bermudez winning 30-27.
At 5-foot-6, Bermudez (8-3) was able to overcome his significant height disadvantage against the 6-1 Garza by taking the fight to the ground repeatedly.
Bermudez was 8 for 8 in takedown attempts.
Garza falls to 11-3 after his second straight loss.