Phil Lo Greco approved as new opponent for Errol Spence Jr.

Welterweight Phil Lo Greco has been toiling in the Las Vegas training camp of junior welterweight titlist Jessie Vargas, sparring with and helping Vargas prepare for his tough assignment next week of moving up in weight and facing former two-division titleholder Timothy Bradley Jr.

Being in shape, nearby and already licensed in Nevada paid off for Lo Greco, who on Thursday was approved by the Nevada State Athletic Commission as the new opponent for heralded prospect Errol Spence Jr. They will meet in a scheduled 10-rounder Saturday night (8:30 ET) in the opening bout of the Premier Boxing Champions card on NBC in prime time at the MGM Grand in Las Vegas.

The card is headlined by the scheduled 12-round, 144-pound catchweight fight between former welterweight titleholders Shawn Porter (25-1-1, 16 KOs) and Adrien Broner (30-1, 22 KOs).

Lo Greco (26-1, 14 KOs) was pressed into service when Roberto Garcia pulled out of the fight Wednesday. Garcia was not close to the 147-pound weight limit, and organizers also said he was dealing with personal issues.

At Thursday's final news conference, Lo Greco said he took the bout without hesitation when it was offered.

"There's no such thing as the right moment. The perfect fight is when you want it to be," Lo Greco said. "I got the call and decided that this is the perfect timing. It took me about 30 seconds to decide to take this fight. When you know why you fight, it makes these decisions easy. A year ago, there was no way I thought I'd be on this stage. Now I have real opportunities, and we're here now. Win, lose or draw, I'm going back to the gym next week."

Spence took the change of opponents in stride.

"I just have to stay focused and put on a spectacular performance," he said. "Hopefully, next time I'll be the main event. It's a process, but I'm getting there. I'm ready for anybody in the welterweight division. I'm ready for any kind of step up in competition, period. I'm not the guy to shy away from anybody. You're going to be looking at the future of the sport come Saturday night."

It is the second time in three scheduled fights that Garcia, who has won nine fights in a row since a decision loss to former titleholder Antonio Margarito in 2010, has pulled out at the last minute with weight being a factor.

Garcia was supposed to fight Porter on March 13 on a PBC on Spike TV card in Ontario, California, until he failed to show up for the weigh-in the day before the bout. The California State Athletic Commission said the reason was because he was at least 4 pounds overweight, although the Garcia camp said he was also ill.

Nevada commission executive director Bob Bennett told ESPN.com on Wednesday that he had some reservations about approving Lo Greco because of his inactivity, but Bennett gave the fight the green light Thursday morning.

Lo Greco, 30, of Toronto, has fought only once in 21 months, winning an eight-round decision against a journeyman opponent in March.

In his previous bout, in May 2013, Lo Greco, a four-time Canadian amateur national champion and 2004 Italian Olympian (who did not get to compete in the Games because of an injury), got knocked down and lost a shutout decision to Porter, who went on to win and lose a world title.

Spence (16-0, 13 KOs), a 25-year-old southpaw from Dallas, was a 2012 U.S. Olympian and is universally regarded as one of boxing's top prospects. He would have been stepping up his level of competition against Garcia (37-3, 23 KOs), 35, of Weslaco, Texas, although Spence was the heavy favorite because he would own significant advantages in speed and skills. For two days' notice, Lo Greco is about as solid an opponent as promoter/matchmaker Tom Brown could have found.

To accommodate for Lo Greco taking the fight on such short notice, the weight limit for the bout was adjusted to 150 pounds. It was 147 before Garcia dropped out.