Oleksandr Usyk and Terence Crawford have valid arguments.

Usyk (24-0, 15 KOs) is a three-time undisputed heavyweight champion in two separate weight classes with two wins each over Tyson Fury, Anthony Joshua and Daniel Dubois. Crawford (42-0, 31 KOs) recently became the first male three-division undisputed champion, and made it look easy against Canelo Alvarez this past weekend.

Bob Arum knows both fighters well. He also respects them immensely. But when it comes to being the best of the best, he reserves that spot for Japan's Naoya Inoue.

“This is the greatest fighter in the world,” Arum told a jam-packed crowd in the post-fight interview Sunday while pointing to the undisputed 122-pound champion.

Inoue wasn’t quite as ruthless as he normally is against Murodjon Akhmadaliev (14-2, 11 KOs) at IG Arena in Japan, but he still found a way to get it done. He boxed, moved, remained on the outside and tamed him with strong right hands when he got out of line.

Arum had the best seat in the house. He smiled as his pound-for-pound star barely broke a sweat. Once the final bell rang, all three judges sitting ringside barely found rounds to give to his opponent, as Inoue (31-0, 27 KOs) cruised to a unanimous decision.

Getting knockouts has almost become Inoue’s signature. Just ask his previous 11 opponents.

With Inoue showing that he's more diverse, Arum believes that took his fighter to another level.

“We saw what a complete fighter Inoue has become,” Arum said. “Not only a great puncher, but great strategy, great footwork. That’s what the real all-time greats have.”

In The Ring's updated ranking released Monday, Inoue actually moved down one spot to No. 3 pound-for-pound to make room for Crawford after his domination of Canelo Alvarez on Saturday.