LAS VEGAS – Vito Mielnicki Jr. sees Alexis Salazar as the most formidable opponent of his four-year pro career.

Mielnicki feels he couldn’t be better prepared for their fight Saturday night, though, after sparring almost a hundred rounds against Jermall Charlo during his recently completed camp in Stafford, Texas. The 21-year-old Mielnicki will fight for the first time against Salazar with Charlo’s longtime trainer, Ronnie Shields, in his corner.

The 10-round, 154-pound bout between Mielnicki (15-1, 10 KOs), of Roseland, New Jersey, and Salazar (25-5, 10 KOs), of Norwalk, California, will be the first of two David Benavidez-Demetrius Andrade undercard fights streamed on Showtime Sports’ YouTube channel from Mandalay Bay Resort and Casino’s Michelob ULTRA Arena (6 p.m. ET; 3 p.m. PT).

“Being 21 years old and being able to spar with [Charlo],” Mielnicki told a group of reporters at an open workout Wednesday, “it’s almost like you’re doing all these rounds with a world champ and then you step in there, it’s like you’re not gonna get anything, you know, higher than what I was sparring and what I was getting in the gym.

“But when you get in there it’s a whole different ball game. It’s 10-ounce gloves, no headgear, and it’s a whole different game once you get in there under those lights.”

Charlo came in 3.4 pounds overweight Friday for his 10-round, 163-pound fight against Jose Benavidez Jr. on the pay-per-view portion of the Benavidez-Andrade undercard. Though overweight and inactive for 29 months, Charlo (32-0, 22 KOs) is an undefeated, two-weight world champion with whom Mielnicki learned a lot during their sparring sessions.

“Jermall didn’t take it easy on him,” Shields told BoxingScene.com. “Jermall really went all out on him. And a couple of times I was saying, ‘Oh, man, let me back him off.’ Then I said, ‘Nah, let me see how he’s gonna react.’ And damn, man, he would come right back. And Jermall said, ‘Man, this kid is good.’ He said, ‘Man, you were lucky to get this kid.’ But it’s just unbelievable work, man, and it was good for both guys. I was really proud of that.”

Shields has also been impressed with Mielnicki’s professionalism and willingness to immediately implement what his respected trainer teaches him.

In Salazar, Mielnicki will encounter a 28-year-old veteran whose last two losses came against WBC interim middleweight champ Carlos Adames (23-1, 18 KOs) and unbeaten junior middleweight contender Xander Zayas (17-0, 11 KOs). Adames stopped Salazar in the third round of their June 2021 bout, whereas Zayas out-pointed him in an eight-rounder last December 10.

Mielnicki became the first fighter to knock out Mexican veteran Jose Sanchez Charles in Mielnicki’s last fight. He dropped Charles (20-4-1, 12 KOs) twice in the third round and once in the fourth round, when their 10-rounder was stopped on the Gervonta Davis-Ryan Garcia undercard April 22 at T-Mobile Arena in Las Vegas.

Mielnicki hopes to stop Salazar inside the distance, too, yet he realizes it won’t be easy.

“I think Salazar is my toughest opponent to date,” Mielnicki said. “He’s been in there with a lotta great guys … it’s another step in the right direction for me. I’m excited to take this step and show the world what I’ve been working on in the gym.”

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.