LAS VEGAS (AP) – Frank Mir is a two-time UFC heavyweight champion with more victories in the division than any fighter. That’s why he knows it’s never been tougher to pull off what he’s trying to accomplish at UFC 146.The UFC is going big in its Memorial Day weekend show, headlined by five heavyweight fights at the MGM Grand Garden in Las Vegas. Junior Dos Santos will make his first title defense against Mir, who marvels at the UFC’s current roster of enormous fighters.“The UFC has always had the best fighters in every weight, but typically in the heavyweight division, (only) the top five was dangerous guys fighting for the title,” Mir said. “The top 10, maybe you’d talk about them in the conversation. I don’t think five or six years ago, we could have had a card that had five bouts of heavyweights fighting — and then we’ve had injuries, too. If we’d had a card five years ago with five heavyweight fights and somebody got injured, the whole card would have had to be scrapped.”Heavyweights jumped to the forefront of the UFC in recent years with the rise and fall of Brock Lesnar, who quit his pro wrestling career and made a high-profile run to the UFC title, stopping Mir (16-5) along the way in July 2009. Lesnar battled injuries and illness, but also struggled to compete with the new wave of dynamic talent arriving in the division, eventually retiring last December after getting pulverized by Alistair Overeem.Mir’s title shot would have belonged to Overeem, but the Dutch kickboxer failed a drug test, clearing the way for Mir to attempt to reclaim the heavyweight belt just two days after his 33rd birthday in a fight with Dos Santos, the Brazilian boxer with humble beginnings and a remarkable MMA pedigree.“It’s a huge moment in my life and career,” Mir said. “Eventually, one day we retire and we’re forgotten as athletes, but people try to somehow make their mark on history. It’ll give me something to brag about to my grandchildren. You know, one time, Grandpa could move from one side of the room to the other without hobbling.”A card stacked with heavyweights is a first for mixed martial arts’ dominant promotion, but all five matchups have changed since the fights were originally announced.Roy Nelson fights Dave Herman, Shane Del Rosario takes on Stipe Miocic and 6-foot-11 Stefan Struve fights Lavar Johnson on the UFC’s first pay-per-view show headlined by five heavyweight fights — more than 2,400 pounds of mixed martial artists, according to UFC President Dana White.Mir realizes the challenge of facing Dos Santos (14-1), who claimed the title last fall with a victory over Cain Velasquez. Mir is a skilled jiu-jitsu practitioner who broke the arm of Antonio Rodrigo Nogueira, Dos Santos’ friend and mentor, in their bout last December, the latest in a career filled with impressive submission victories.Mir believes he’s much better on the ground than Dos Santos, but the Brazilian has spent exactly 13 seconds on his back during his MMA career. Nobody has been able to take down Dos Santos, whose striking abilities make it dangerous to even get close enough to try.“He’s very impressive, and he’s probably a better boxer than me, but so what?” Mir asked. “I know I’m better on the ground, and I’ve got to figure out a way to prove it, and I’m going to.”The genial Dos Santos has exchanged some seemingly halfhearted trash talk with the erudite, loquacious Mir during the promotion of their bout, but he appears confident in his ability to outslug anybody after his 64-second victory over Velasquez. Dos Santos scoffs at the notion Overeem might have been a tougher matchup for him than Mir, who was stopped by punches in each of his five career defeats.“I know he’s a guy who has been around a long time and knows how to do everything,” Dos Santos said. “I’m going to see if he can handle what I can do, and I’m going to try to knock him out in the first two rounds.”Moments before Dos Santos meets Mir, Velasquez (9-1) will attempt to get his career back on track when he meets Antonio Silva, the veteran Brazilian super heavyweight making his UFC debut. Velasquez, the former Arizona State wrestler, hasn’t fought since Dos Santos pounded him in Anaheim last fall, blemishing his previously perfect record.“I’m definitely able to let it go,” Velasquez said. “In wrestling, I’ve lost matches before, so it’s always a thing where you learn from it. You just watch film, but you don’t really keep it with you and always think about it. I wasn’t thinking that I was going to go through my entire career undefeated.”The undercard features popular middleweight Jason “Mayhem” Miller, who says he’ll retire if he doesn’t defeat C.B. Dollaway, another former Arizona State wrestler. Unbeaten lightweight Edson Barboza, English veteran Dan Hardy and former WEC featherweight champ Mike Brown also will fight at UFC 146.