Trainer Derrick James believes Terence Crawford’s abilities in the ring are mostly the result of his gifted physical attributes.

The veteran trainer of unified WBC, WBA, IBF welterweight champion Errol Spence Jr. thinks the WBO titlist from Omaha, Nebraska, is a particularly difficult adversary because of his athleticism, more than, say, his skills.

The three-division titlist Crawford (39-0, 30 KOs) and Spence (28-0, 22 KOs), of Desoto, Texas, are set to fight each other July 29 at T-Mobile Arena in Las Vegas for the undisputed welterweight championship on Showtime Pay-Per-View.

“I think that throughout the fight, I think he had a great game plan,” James said of Crawford’s win over Shawn Porter during a segment on Episode 2 of All Access on Showtime. “Terence, what makes him dynamic is that he’s very elusive and he’s very—he’s able to use his arm length and distance. He’s really more athletic than he [has] boxing skills.

“He’s very athletic, very fast, very quick-twitch muscles. That’s what it is, his athleticism.”

James—who, in addition to Spence, trains undisputed 154-pound champion Jermell Charlo, former heavyweight titlist Anthony Joshua, and lightweight contenders Frank Martin and Ryan Garcia—pointed out that Crawford, 35, will have to show a new wrinkle in his game when he goes up against a punisher like Spence, 33.

“He’s a great threat,” James said of Crawford, “but you can’t judge the depth of his desire until you get in the ring because it’s like Errol’s hitting him, breaking ribs, breaking your orbital bone, you keep fighting, breaking you nose, you can’t see that from his record. But on paper, he is the most accomplished fighter in boxing. I think that there comes a point where someone’s breaking you, how much do you really want it? And that’s what we’ll see.”