Berto steps between the ropes just six months after failing a drugs test ahead of his rematch with Victor Ortiz, to take on the WBC welterweight champion.
Guerrero has stepped up two weight divisions to make his voice heard after time out to help his wife overcome leukaemia.
And Berto admits he only has respect for his opponent heading into the contest in Ontario, California.
"This has been a long time coming," said the former champion. "I've had a hell of a year, going through a lot of trials and tribulations.
"I believe that everything happens for a reason and I've learned a lot about myself and how strong I am to get through what I've been through. I'm in a whole other mind frame and have a whole new motivation.
"I had a tremendous training camp and I'm in the best shape that I've been in in a long time. I'm focused and I think that's the most important thing.
"I want to thank Team Guerrero for taking the fight. He's a tough opponent and you definitely have to respect him for going through what he's been through with his wife.
"I'm in shape and I'm ready to get back out there under the lights and have fun like I used to."