There’s a stoic, almost cautious nature to unbeaten junior welterweight titlist Viktor Postol’s personality, which mirrors his calculated style inside the ring.

“I’m a little hesitant and I’m not too talkative,” Postol told ESPN.com, with the help of translator Vadim Kornilov. “I enjoy that. That’s part of the way I am.”

It’s not that Postol (28-0, 12 KOs), appropriately nicknamed “The Iceman,” isn’t exciting. In fact, if you watch him compete long enough, he has a way of coming out of his shell at just the right moment — evidenced by the explosive way he finished Selcuk Aydin and Lucas Matthysse in a pair of victories that put Postol on the map in the United States.

A native of Ukraine who didn’t compete outside of Europe until his 20th pro fight in 2012, Postol certainly prefers to approach you on his terms, at the tail end of a well-considered plan of attack. It’s a good way to describe his journey from being an unknown to a fighter who is on the verge of making major noise in the sport.

Postol, 32, squares off with Terence Crawford (28-0, 20 KOs) at the MGM Grand in Las Vegas on Saturday (HBO PPV, 9 p.m. ET) in a unification bout for 140-pound supremacy. Crawford, ESPN.com’s 2014 Fighter of the Year, enters the bout ranked as ESPN.com’s No. 6 pound-for-pound boxer in the world.

Ask Postol about the high stakes or Crawford’s skills and, true to his nature, the Ukrainian is unmoved. He describes his placement in this pay-per-view main event as simply “payback for how much I put into the sport and how much I have worked hard to make sure to get to my dream.”

But if you ask Postol for the turning point in his career — the exact moment when his seemingly unshakable confidence was set in stone — you can hear a slight change in his reticent voice.

Freddie Roach, who became Postol’s trainer before his May 2014 fight, flew Postol to the Philippines to spar with Manny Pacquiao at his gym in General Santos City. Pacquiao — with his longtime trainer, Roach — was preparing for a November 2014 pay-per-view bout against Chris Algieri, and Postol fit the bill as a tall, rangy fighter with a pure boxing pedigree to mimic Algieri.

At the start, however, things didn’t go smoothly for Postol.

“In the beginning, Manny got the best of Viktor,” Roach said. “But as camp progressed, so did Viktor.”

Roach said Postol was a quick study and adapted to Pacquiao’s frenetic style.

“[It was] to the point that both were even with each other when they sparred,” Roach said. “When that happened, I stopped having them spar with each other so much. I didn’t have to teach Viktor anything special about sparring with Manny. Viktor taught himself how to adapt and counter to Manny’s style. It was very impressive.”

Postol credits his 2011 victory over Karen Tevosyan in his native Ukraine — for the WBC International Silver title — with planting the seeds of confidence that he can compete at the elite level. But it wasn’t until he sparred with Pacquiao that it all sunk in — that moment when Postol realized just how great he could be.

“That was the second step for me in understanding and realizing I can fight anybody in the world, because I felt pretty confident,” Postol said. “When I was sparring, it built my confidence up even more.”

Postol’s in-ring style might best be compared to that of a chess player, who sets up his moves well in advance.

“I would say about my style that I’m not in a hurry,” Postol said. “I know that the fight is a 12-round fight, and I want to make sure that I don’t make any mistakes — and I feel everything out and make my moves late. There is no reason to be too much in a hurry because it can be grounds for a mistake.”

Postol is just another in a line of skilled, tough fighters from Eastern Europe who have taken over boxing in recent years, joining the likes of Sergey Kovalev, Gennady Golovkin and Vasyl Lomachenko. When asked for the secret to their success, Postol pointed to one thing: hard work.

“I think it has something to do with the history of our countries,” Postol said. “I think some of the Russian and Ukrainian fighters are just very persistent and the work ethic is very, very high and somewhat different than other fighters. I think that work ethic is a big part of the achievement.”