Luke Rockhold doesn't come right out and use the word "cheater" when referring to his opponent on May 18.
But the final Strikeforce middleweight champion doesn't really need to. As far as Rockhold is concerned, Vitor Belfort's build simply doesn't pass the eye test.
"Just look at his physique," Rockhold said in a recent one-on-one interview with Yahoo! Sports. "Look at how he looks at [36 years old]. You can't tell me that at his age, something like that looks natural."
Belfort is one of a handful of fighters in their 30s and beyond – along with the likes of Chael Sonnen and Dan Henderson – who experienced career resurgences after undergoing testosterone replacement therapy (TRT), a controversial-but-legal treatment.
Rockhold, though, isn't buying it.
"TRT use is something I don't agree with at all," Rockhold said. "It's a way to get around the system. They say TRT is needed for low testosterone, that it's a medical condition. Well, what causes low testosterone? Prolonged steroid use is one cause."
[Related: Vitor Belfort defends TRT usage]
Belfort was suspended by Nevada for nine months in 2006 after testing positive for the banned substance 4-Hydroxytestosterone after a loss to Henderson in a Las Vegas PRIDE card.
"It's frustrating to someone like me, who's fought clean, has no reason to cheat, and has done things the right way," Rockhold said.
The TRT talk has created a charged atmosphere for Rockhold's first UFC fight, which is the main event of UFC on FX 8 in Jaragua do Sul, Brazil. For his part, Belfort, a Rio native, hasn't taken one step backward from Rockhold's assertions.
On Monday, he told MMAFighting.com he considers Rockhold's words disrespectful. "I don't know what he did in the sport," Belfort (22-10) said. "I think it's disrespectful, the way that he thinks. "But it is what it is. You cannot control it, you cannot control people."
A product of The American Kickboxing Academy in San Jose, Calif., the MMA home of Cain Velasquez, Daniel Cormier, Josh Thomson, and Jon Fitch, Rockhold first made waves in the sport by recording his first seven career victories via first-round finish.
But then the 28-year old Santa Cruz native had to sit through a couple periods of prolonged inactivity. First, there was a 17-month span in 2010-11 in which a shoulder injury kept him out of action. Then, after winning the Strikeforce middleweight title, he's only fought once in another 17-month stretch, as he, along with the rest of the company roster, watched from the sidelines as the company died a slow, painful death.
"Success in this sport's so much about momentum," Rockhold (11-1) said. "It's tough sitting out on the sidelines like that. That's when I most appreciate being a part of a gym like AKA, where you've got someone like Cain, who's dealt with a major injury, someone like Daniel who's been through the ups and downs… coaches who have been there and done that."
As if the war of words over TRT weren't didn't already add intrigue, Rockhold admits to carrying a bit of a chip on his shoulder on behalf of his former company. Former Strikeforce fighters like Cormier and Thomson have made successful UFC transitions in 2013. Even those who have come up short, as former Strikeforce lightweight champion Gilbert Melendez did in a split decision against UFC champ Ben Henderson, have acquitted themselves well in defeat.
"To this day, you hear it," Rockhold said. "You go online and you see people putting down what you accomplished in Strikeforce, and they say things like 'you're in the UFC now, they're going to put you in your place. At this point it's like, have you even been watching the fights? Did you see what Josh did to [Nate] Diaz? So yeah, it's a little bit of extra motivation to prove I belong."
With a 10-fight win streak, few question whether Rockhold belongs. But a victory would cement his place. For all the heated talk between the two, Rockhold still respects what Belfort, who made his UFC debut as 19-year old billed as "The Phenom" at UFC 12 in 1997, has accomplished in the sport.
"He was one of the very first fighters I followed as a fan," Rockhold said. "He's on the short list of guys, including Randy Couture, who inspired me to give fighting a try. The closer we get to the fight, the more real it becomes. I don't agree with the choices that he's made in recent years, but I can't deny what he's done in the sport.
Belfort's only losses since 2007 have been to current UFC champions Anderson Silva and Jon Jones. He rebounded from his September loss to Jones with a head-kick finish of Michael Bisping in January.
"There's a reason I wanted Belfort," Rockhold said. "I didn't want a tune-up fight. I didn't want an easy fight. I asked for this fight, when Vitor beat Bisping I saw a window of opportunity. I didn't want to sit around and wait forever.
"I want to take on the best, make the best impression, and show that I'm worthy of a title shot. Vitor's still got his heavy hands, I respect that and I'm cognizant of it, but I'm confident I can take this fight anywhere he wants to take it. I can win the fight standing and I can win it on the ground."
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