Since that defeat, Klassen is 4-0, all victories inside the distance, and he says he hasn't made the trip to Texas to see that streak end.
"For me to come to Houston from South Africa and leave my title here is not going to happen," Klassen said. "That will never happen."
Klassen is counting on his first fight in the United States to be a springboard to fame in North America.
"This fight will open up doors," he said. "I'm not a person who needs a lot of money. I just want to make my name."
Guerrero, a two-time featherweight world champion, moves up a division to challenge Klassen.
Guerrero is no stranger to tough fights. He won a title fight in Denmark before hostile fans, and has fought throughout his wife's ongoing battle with leukemia.
He brings a record of 24-1-1, with 17 knockouts, But his no-contest against Daud Yordan, when he said he couldn't continue because of a cut, sparked questions.
"The one area where Guerrero is going to be tested is in the heart department, and we've noticed the heart isn't too big," Klassen trainer Nick Durandt said.
Former lightweight titlist Diaz (34-2, 17 KO), has lost two of his last three, including a knockout loss to Juan Manuel Marquez in February.
Source: AFP American Edition