Three years later in a rematch, the outcome was more definitive, a second-round stoppage against the aged four-division champion.

Many expect Inoue (32-0, 27 KOs) to have the hardest fight of his career when he defends his undisputed junior featherweight title against Japanese countryman Junto Nakatani (32-0, 24 KOs) on Saturday at Tokyo Dome on DAZN, which will begin its undercard coverage at 5:40 a.m. ET in the U.S. and 10:40 a.m. BST in the UK.

Donaire, now 43 and still active as a bantamweight, sees the slugfest between buzzsaws as a seesaw that can tilt on either side.

The Ring interviewed Donaire before the mega matchup to get his analysis as two of the world's best pound-for-pound stars collide. The interview has been edited for length and clarity, and the following is Donaire’s words.

This is one of the best fights of the year. Both guys really are out for each other, and it's a must-watch fight. It’s a very interesting fight because both are at the very top of their capabilities. There's a very big difference in terms of how the fight can look because we know that Inoue can fight, punch and has great speed.

One thing that Inoue has been blessed with is his ability to fight and hit hard. But a lot of the fighters that he's fought are very afraid of him. I believe that changes with someone like Nakatani, who's unafraid and can change the dynamic of how he fights. Nakatani can make this a whole different level of fight.

Nakatani is coming into this fight as the underdog when he's always been the top dog. Nakatani has the height, he's a southpaw and not afraid. Those three factors can change how Inoue's fight can look. But in his last fight, Nakatani had difficulty with a rugged guy in Sebastian Hernandez, who kept coming in.

Inoue has the power and speed to cut distance, and that can be a big problem for Nakatani. Not only that, but the body shots. Being a taller guy, you're very vulnerable to being hit with body shots, especially coming from a guy like Inoue, with the power, speed, timing and distance management to close in quickly.

Nakatani needs to continuously use his straight as a jab – that would be the key to beating Inoue. So that way, it stops Inoue from coming in because it'll be right down the middle, compared to using the jab, where Inoue can slip it and get in. But if you throw it straight, it puts him in an angle where he can shift off or step back and not be in harm's way. Nakatani needs to fight at a far distance rather than take over and try to close in. That's gonna be a detriment to his style.

I don't think Inoue is getting old at 32. Not for this Nakatani fight – there's a rivalry between them, and who’s going to be the best in Japan.

It's a very interesting fight because both guys have the ability to beat each other. I don't think this fight is that wide because when it comes down to it, we've seen that Inoue gets hit with the left hook. We see that vulnerability. Luis Nery and Ramon Cardenas knocked him down, I hurt him, and it’s all been coming from the left hand.

The southpaw stance is more dangerous for Inoue than what he's so used to. He hasn't fought enough southpaws to be able to feel comfortable, as he has with orthodox fighters.

Inoue will have problems adjusting to the height and Nakatani's southpaw stance. Nakatani has the advantage in the early rounds because Inoue is going to try to figure him out. But again, Inoue is the kind of guy who goes in there trying to knock you out in the early rounds and his fights can be very short.

It's hard to gauge if Inoue was the hardest fight of my career, knowing my capabilities at the times that I fought him, and what my best was. Ultimately when it comes down to skills, Inoue is one of the best fighters that I've fought and could be the toughest guy as well.

Inoue's power is one high factor that makes him special, because it takes away a lot from his opponents' will to fight. He has amazing timing and those quick movements. He's not quick all around, but when it comes down to attack. Sometimes that's all he needs – to be able to close the distance in a very short amount of time.

Those factors make him very dangerous.

Both guys are capable of beating one another. Inoue is capable of beating anybody out there, but Nakatani does too. So will it be the passing of a torch? It's possible, Nakatani has a chance to beat Inoue and I believe he can.

It comes down to who can utilize their style to win the fight. Whoever can create that in the early rounds will set the tempo and win.