He's a natural athlete despite his body shape, but that's changing, too. He has lost a significant amount of weight under Sanchez's demanding schedule, but his relative lack of reach could hurt him against Parker.
Kevin Barry will want the 24-year-old Parker to fight on the outside against Ruiz, who has promised "fireworks" and a pressing, suffocating style at Vector Arena on December 10. Parker has become better at following Barry's game plans, and attention to detail will be crucial in the biggest fight ever to be held in New Zealand.
Another big advantage for Parker, who enjoys fighting aggressive, hard-charging opponents, is that he is fighting at home, at a place where he is comfortable.
Ruiz, who has fought twice in Macau but never in the Southern Hemisphere, said he didn't know much about New Zealand. He will arrive a fortnight before the fight.
He was familiar with Tua, though, the Samoan-New Zealander who paved the way for Parker.
Tua lost his fight against Lewis by decision but enjoyed many highlights in a 59-fight professional career. He won 43 of his fights by knockout and had fearsome power, particularly when unleashing his left hook.
"He was a beast, man," Ruiz said. "It would have been scary to be in the ring with him. He had a lot of power. He was short as well. David Tua was a heck of a fighter."
Ruiz has handled his media commitments with charm and good humour so far - but the fight build-up will put the spotlight on him like never before.
Parker has become used to being in the spotlight, but Mexican-born Ruiz doesn't seem to be.
His trainer, Sanchez, said the winner will see his career go to a new level.
"That night, a star is going to be born because I think it's going to be a fight where people take notice," he said. "These are two guys with very good skills that have not really been exposed to the public."
Patrick McKendry travelled to Las Vegas with assistance from Duco Events.