Saul 'Canelo' Alvarez acknowledges he faces the biggest test of his career on November 2 when he steps up two weight classes to take on Sergey Kovalev.
Alvarez is a three-weight world champion and is now bidding to take the WBO light-heavyweight belt from champion Kovalev.
The Mexican has lost only once in a 55-fight career (52-1-2) but recognises the difficulty of facing a bigger man and a fellow established star.
"I'm very motivated here," Alvarez told a news conference. "It's an honour for me to share the ring with a fighter like Kovalev. Now we're about to make history.
"I know it's going to be the most difficult fight of my professional career. I'm going to put all of my strength and effort to give the best that I can in the ring."
Kovalev described Canelo as "one of the best fighters in the world" and said he was "happy and really excited", while Buddy McGirt, his trainer, paid tribute to both fighters.
Canelo's trainer, Eddy Reynoso, realizes the risk in front of them. When the two fighters came together for their press conference, Kovalev dwarfed the much smaller Canelo.
It was only a few years ago when Kovalev was viewed as one of the most feared and deadly punchers in the sport.
"The big fighters? Only the ones who leave a footprint become these kind of fighters," said Reynoso.
"We know Kovalev well and we know the challenge that we are facing. He is a great fighter who leaves everything in the ring.
"With one punch, he can end the fight. We want Saul to have the four championships."
Canelo, the reigning world middleweight champion, said: "I know it will be the most difficult fight of my [career]."
Kovalev (34-3-1) is returning to the United States, fighting in Las Vegas, after surviving a scare against Anthony Yarde back in Russia last month.