NEW YORK - Staring up at the imposing Wladimir Klitschko during the weigh-in two days before their heavyweight unification fight, Sultan Ibragimov barely batted an eye.

This wasn’t just boxing bravado, though. The relatively unknown, largely undersized WBO champ has made a habit of felling bigger foes.

Going all the way back to the 2000 Sydney Olympics, when the 6-foot-2 Russian southpaw lost a controversial decision to Cuban great Felix Savon in the gold medal match, Ibragimov has had to rise to the occasion. Literally, in almost every case.

Shannon Briggs had more than 50 pounds on Ibragimov, but the American couldn’t catch up to his constant movement and fast hands. Javier Mora, Lance Whitaker, Andy Sample — all of them had more than 30 pounds on Ibragimov, and all of them lost in lopsided fashion.

“People say this is a big guy and I’m a small guy, but you’re going to see a great fight Saturday night,” said Ibragimov, who weighed 219 pounds Thursday against a svelte 238 for the IBF champion, in what will be the first heavyweight unification bout since 1999.

“(The size difference) is something I can’t control anyway.”

Klitschko (49-3, 44 KOs) arguably carries his weight better than any of those other guys. Better than his opponent at Madison Square Garden, for that matter.

Whereas up-and-coming trainer Jeff Mayweather appeared to mold Ibragimov out of putty, creating a well-rounded boxer out of a brawler, Klitschko looks like a heavyweight champion out of central casting — like Hall of Fame trainer Emanuel Steward shaped a slab of concrete with a chisel and hammer.

When Klitschko, at his lightest since 2000, and Ibragimov (22-0-1, 17 KOs) were told to stand face-to-face for photographs, it comically wound up more like face-to-chest.

“He made it, he’s undefeated and he’s a champion. It speaks for him and to him,” Klitschko said. “He doesn’t look maybe impressive, but he’s very effective in what he’s doing.”

Ibragimov has tried to put on weight before, but the one time he tipped the scales above 230 he was sluggish in a draw against Ray Austin.

Mayweather jumped aboard soon after and immediately set about trimming 10 pounds from his charge. By the time Ibragimov fought Evander Holyfield last October, he was back down to 219 pounds and easily outpointed the former world champion.

“He’s used to being a small guy. His whole life is that role,” Steward said. “He likes to have big guys get out of position and then he explodes on them. And then he moves away again and takes his time and keeps a little space.

“He’s used to fighting big guys so he knows what to do. It’s not like he’s a guy who’s just been fighting guys his own size.”

Klitschko’s typical size advantage hasn’t always helped, either.

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In his last two losses, to Corrie Sanders in 2003 and Lamon Brewster 13 months later, he carried 17 pounds more than his opponent. Klitschko also had a big size advantage on DaVarryl Williamson, but was barely ahead when referee Jay Nady sent it to the judges after the fifth round in 2004 because an inadvertent head butt had opened a gash above Klitschko’s eye.

Steward thinks his Ukrainian fighter is better than he’s ever been, though, and perhaps better than anybody’s ever been.

Tall praise from the legendary trainer who helped guide former heavyweight world champions Holyfield, Lennox Lewis and Michael Moorer.

“Very few guys are going to match Wladimir with just pure strength,” Steward said. “Even guys that are as big as him don’t have the strength.”

It’s unlikely Ibragimov plans to deal in power punches. The 32-year-old fighter will more likely use his quick combinations and lateral movement, darting in to deliver a couple of punches before backing out of range.

That’s the plan, at least.

“You have to fight Wladimir’s arms before you can fight Wladimir,” Steward said. “He’s a master at controlling distance with his arms, so he won’t get in. The strategy for Wladimir is pressure. The other guys let (Ibragimov) take a holiday, but Wladimir is pressure and Wladimir is faster on his feet than everybody understands.”

Speed to go with that size?

It’s a wonder oddsmakers have Ibragimov only a modest underdog.

“I am going to win the fight. I am determined to win this fight,” Klitschko said. “The fight is scheduled for 12 rounds, but I doubt it will go the distance.”