Amir Khan says his bout with Carlos Molina is a "make or break fight".
The light-welterweight lost his last two fights and will struggle to maintain his status as one of boxing's big draws if he loses in California on Saturday.
It will be the first time he has fought since he started working with trainer Virgil Hunter.
He said: "I know it is a make or break fight for me, that's why I'm taking it so seriously."
Khan's career is at a critical point as he prepares for the bout at the Los Angeles Sports Arena.
He was knocked down three times in defeat by Danny Garcia in July and now has a 26-3 record.
The Bolton-born boxer, 26, said: "We will be more than ready for this fight and we will be in the best condition ever.
Khan is determined to beat the California-based Molina by a convincing margin having controversially lost a points decision to Lamont Peterson in Washington a year ago - one of two successive defeats.
Khan, a 2004 Olympic lightweight silver medallist, intends to change to a more defensive style after being caught by punches when attacking opponents in his last two fights.
He added: "It is always tough to fight someone in their back yard and maybe that is why we are training even harder.
"It has been a tough road. We have fought some big names.
"It is going to be another tough fight. We are going to go in there and do what we do best.
"A win is a win and I will be sticking to the plan and sticking to the instructions from the corner instead of getting too wild.
"People will still see an exciting Amir Khan, but now I'm a more mature fighter."
Orthodox fighter Molina, 27, is unbeaten in 18 fights but has boxed mainly in his home state of California.
He a lightweight stepping up a division and is four inches shorter than his opponent.
And his description of the bout as a 'shot at the big time' underlines his lack of top-level experience.
Molina said: "I am willing to walk to hell and back. This is my shot. This is my opportunity.
"I have to be smart about it. I can't go in there and attack, attack, attack. I have to be smart about it.
"He is a good boxer. We have a good plan for him and we are going to execute it on Saturday."