When Diego Sanchez (21-3 MMA, 10-3 UFC) steps in to the cage against John Hathaway (12-0 MMA, 3-0 UFC) at Saturday night's UFC 114 event in Las Vegas, it will be the first time "Nightmare" has competed at welterweight since a June 2008 win over Luigi Fioravanti.

Sanchez made the move back to 170 pounds after a failed lightweight title bid against B.J. Penn at UFC 107 this past December.

A winner of the original "The Ultimate Fighter," Sanchez said the return to 170 pounds was always in the cards, and though he's done with lightweight for now, he feels there's unfinished business with Penn.

"The decision was always made before I even went down," Sanchez told MMAjunkie.com (www.mmajunkie.com). "When I made the decision to go to lightweight, I knew it was going to be a brief hiatus. My goal was to go down, do something that no one has ever done before: fight two fights, win the belt and go back up.

"B.J. Penn caught me in the fifth round, and I was unable to continue. That was a very bad cut. I would have loved to have continued and finished the fight, but when the doctor says you've got to stop, you've got to stop. That's what I had to do."

Penn retained the belt after a fifth-round high kick opened a gash on Sanchez's head. The champion controlled the action from the outset, though Sanchez courageously battled until the final frame.

Now Sanchez says he hopes for a rematch if and when Penn makes his much-anticipated return to the 170-pound division.

"B.J. did a great job," Sanchez said. "He trained probably harder for me than he did for any other fight in his career. He was a game B.J., and I was a game Diego. He outpointed me. He outboxed me, and I was unable to take him down, and I lost the fight fair and square.

"That's my dream, to get a rematch with him, but at 170. But one can only take their career one fight at a time, and right now that's John Hathaway, and I'm extremely confident for this fight with John Hathaway."

An undefeated British fighter, Hathaway fights in the U.S. for the first time in what is unquestionably the biggest fight of his career. While Sanchez has seen tape of Hathaway's UFC wins over Paul Taylor, Rick Story and Thomas Egan, he admits to knowing little else about his foe.

"I don't really know John," Sanchez said. "I don't really know much about him besides watching his fight tapes. I tried to investigate him a little bit, but he doesn't Twitter or Facebook. He just seems like a young kid that is definitely tough. He played rugby and then came to our sport.

"I think in his mind, it's a win-win situation to fight me. I'm just happy he came in and took the fight. Every undefeated fighter has to lose a fight sometime, and I'm going to be the one to put that first loss on his record."

While Sanchez views Hathaway's position as a win-win proposition, the 28-year-old doesn't believe he's under any added pressure. In fact, at 7-0 in Las Vegas fights during his career, Sanchez said he feels right at home.

"I don't feel the pressure on me," Sanchez said. "The pressure has always been on me. I'm used to it.

"I think with him coming from the U.K. for the first time and fighting at MGM – I don't know if he's ever even watched a fight at MGM, but when it's sold out, it's something else. The energy is crazy. Las Vegas is my city. I'm undefeated over here in Las Vegas. I've got a huge fanbase following me, and I just love to come and fight over here."

So Sanchez returns to his 170-pound home and looks to make a run for the welterweight title. But if you think he might have shed a little too much weight in an effort to compete at 155 pounds, think again. Sanchez said he's put all the muscle back on – and then some.

"While my cut was healing up for those three months, I couldn't really train, so I did a lot of lifting and got my weight up," Sanchez said. "I did a lot of squats, got the powerlifting up. I got my strength up.

"If I'm going to deal with these big guys at 170 (pounds), I've got to be able to match their strength and size. I'm still cutting like 16 pounds for this fight, so I'm not in any way an undersized welterweight."