Naoya Inoue, the best pound-for-pound boxer you've probably never seen

Naoya Inoue has torn through three weight classes without losing his knockout power, accumulating 15 knockouts and a 17-0 record, including this May 2018 win over Jamie McDonnell. Shuji Kajiyama/AP Photo

Whether or not you take pound-for-pound lists in boxing seriously, one thing you'll immediately notice about those rankings nowadays is that either unified lightweight champion Vasiliy Lomachenko or welterweight world titleholder Terence Crawford sits at No. 1. That duo is typically followed by the likes of unified cruiserweight champion Oleksandr Usyk and unified middleweight champ Canelo Alvarez.

But WBA bantamweight "regular" world titleholder Naoya Inoue, of Japan -- currently rated No. 7 by the ESPN panel -- could be the most dominant fighter in the world that many fans have never had the opportunity to see fight.

Perhaps it's because he has been fighting in the smaller divisions in Asia for the most part, having begun his career as a junior flyweight (108 pounds). But those in the boxing world who follow the sport closely understand just how good "The Monster" really is.

"I rank him as No. 1," said trainer Rudy Hernandez, who has one of the sharpest set of eyes in the game. "[Inoue is] a guy who has challenged the best champions in [each] division and he's gone up three divisions and he's knocked guys out.

"The reason I put him above Crawford and Lomachenko is that he goes in there with the intentions of hurting people and leaving no doubt in the fight."

The case for Inoue, who faces IBF bantamweight titlist Emmanuel Rodriguez (19-0, 12 KOs), of Puerto Rico, in the World Boxing Super Series semifinals Saturday night at the SSE Hydro in Scotland (DAZN, 2 p.m. ET), is that he hasn't just won belts in three different divisions. In the age of multiple sanctioning bodies, many fighters have been engineered to win titles in various weight classes by picking and choosing soft spots, but it's rare that a boxer is considered one of the best in each division that he has competed in.

His overall resume over 17 professional bouts (17-0, 15 KOs) is impressive.

"My aim is a KO in any fight," Inoue told ESPN.com. "In my last two fights last year, that moment just happened to come in the first round. My goal is not to finish the fight in the first round, but [I] will go for the KO when I see the chance."

Inoue began his career in 2012 with a fourth-round KO of Crison Omayao. In his fourth fight, Inoue defeated Ryoichi Taguchi -- a veteran of 20 bouts at the time, who had a record of 18-1-1. Taguchi eventually became a junior flyweight world titleholder, made seven title defenses and unified the WBA and IBF belts during his reign.

Two fights later, in 2014, Inoue stopped Adrian Hernandez in Round 6 to win the WBC junior flyweight world title. After one defense, Inoue skipped the flyweight class to challenge WBO junior bantamweight world titlist Omar Narvaez, who in 45 professional bouts (where he amassed a record of 43-1-2) had never been stopped.

Inoue needed only two rounds to defeat Narvaez by KO.

After seven defenses Inoue, 26, moved up last May and stopped Jamie McDonnell in Round 1 to win the WBA "regular" bantamweight belt. To put this into perspective, McDonnell had never been stopped in more than 30 professional fights.

Inoue's first defense came in the opening round of the WBSS -- a fight in which he knocked out the normally durable Juan Carlos Payano in the first round. Payano, a former belt-holder at bantamweight, had never suffered a KO loss in his career.

To date, 12 of Inoue's 17 professional bouts have been title fights. There have been seven boxers who had never been knocked out before facing Inoue, who failed to see the final bell against "The Monster." Along with Narvaez, McDonnell and Payano, Yuki Sano (TKO10), Ricardo Rodriguez (KO2), Antonio Nieves (TKO6) and Yoan Boyeaux (TKO3) all suffered their first stoppage defeats at the the hands of Inoue.

Fighting out of his tall, upright orthodox stance, Inoue creates an unbelievable amount of torque from his legs that give his punches a whipping effect. His punches aren't so much thrown, but seemingly thrust from a cannon. He has a booming right hand and a left hook to the body that would make Julio Cesar Chavez proud. At times, he seems to come out of his shoes as he punches, but he is able to keep his balance and maintain his defensive integrity.

According to Hernandez, who is the lead trainer for another Japanese world champion, Masayuki Ito, it isn't just that Inoue is blessed with power.

"His timing, he has a good eye, he just seems to be a step ahead of everybody," Hernandez said. "He has those fundamentals, he is a good boxer. I think he has the whole package."

Nieves (18-2-2, 10 KOs), who faced Inoue in 2017 at the StubHub Center in Carson, California, speaks glowingly of him.

"He honestly is a great fighter and I would say [a top] pound-for-pound [boxer]," Nieves said.

Nieves recalls that as he was hit early on by a clean shot from Inoue, he immediately became a believer in Inoue's vaunted power.

"He punches hard and he punches fast,'' Nieves said. "Sometimes you run into guys that are great punchers but are not really quick, so you can't adjust. Sometimes you run into guys who are really quick but can't really punch, so you can adjust.

"But this kid just has it all. He's quick, he has great leg movement, good footwork. He's just a great overall fighter."

Nieves, who was born in Cleveland but has a Puerto Rican background like Rodriguez, has realistic expectations about what kind of chance Inoue's challenger has this weekend.

"Even though I'd like to see my fellow countryman win, it's going to be hard for him," Nieves admitted. "In that first fight in the tournament [versus Jason Moloney, Rodriguez] was getting hit cleanly -- and I believe that if Inoue hits you clearly as many times, you're going to go out."

Should Inoue defeat Rodriguez, he will then face a future Hall of Famer, Nonito Donaire, in the WBSS bantamweight finals. It's a fight that Inoue is expected to win, and would add another notable name to his hit list.

And then after that?

"He can move up to 122," said Hernandez, ''and do very well there."