Anthony Joshua has stopped using his mobile phone - so that he can see Andy Ruiz Jr's punches coming.
The Brit defends his three world titles against Ruiz at Madison Square Garden on Saturday night.
And he respects his opponent's hand speed enough to put down his gadgets.
"If you watch some of his fights a lot of his knockouts have come from combination punches," Joshua told Sky Sports .
"And I feel like it's the punch you don't see that hurts. And Ruiz Jr has got speed in both hands.
"So I have got to make sure I work on my reactions - staying off my phone to make sure that my eyes aren't too tired because I've got to stay sharp with my eyes and how I react to these type of punches."
Ruiz Jr's previous challenge for a world title - against Joseph Parker three years ago - ended in a points defeat.
He has fought just three times since against moderate opposition, winning all three.
And Joshua insists he is wary of the Mexican American.
"His strengths are his ability to come forward and absorb punishment and avoid punishment, as well," he added.
"Because a come-forward fighter seems to walk into punishment - he doesn't take too much stick.
"He can knock guys out so that means he's heavy handed.
"He has the ability to throw combination punches whereas I feel like the European style that I have been taught is 'jab, one, two, jab, one, two, hook'.
"But he can throw left hook, right hook, left hook, right hook, uppercut, hook, right hook to the body.
"So he's got many strengths. But one of his many strengths I would say is that he put his name on the dotted line. Where many people didn't, he did, and that shows me strength in itself."
