Amir Khan's trainer had reservations about the upcoming bout with Saul "Canelo" Alvarez.
The WBC middleweight title bout was announced in February, with some surprised that Khan would fight above welterweight for the first time, and against such an experienced opponent.
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Khan and Alvarez will meet in Las Vegas on May 7.
"Initially I wasn't for the fight. What changed my outlook on it was Amir's response to me when I asked him, do you want this fight," trainer Virgil Hunter said in a media conference call on Tuesday.
"His response to me was quite assuring that he understood what he was going up against and what he was getting into, so off that I felt much more confident in his ability to be competitive and win this fight.
"You have to be impressed. It's a step that not many fighters would take under those circumstances. He's got more than just some balls, he's got audacity."
When asked why he was concerned at first, Hunter replied: "Size difference, first and foremost.
"And the fact that Amir had been off for a while, Canelo had been fighting quite regularly and he's been getting into a groove.
"But we're not just hoping it goes our way, we're approaching it determined for victory and to make it go our way and that's the approach."