The tough-talking Puerto Rican will attempt to take Calzaghe's crown on Saturday 17 August at Cardiff Castle, but believes the Welshman will not take him seriously because he is a late replacement.

Jimenez was only confirmed as Calzaghe's challenger on Monday after the late withdrawal of American David Telesco.

But 32-year-old Jimenez, who is based in Las Vegas, is in top shape as he was already in training for a fight before getting the call from Calzaghe.

The WBO's No 3 ranked challenger and Latino 168lbs champion believes he has the tools to end Calzaghe's four-and-half year reign as world champion.

Calzaghe will be making his 11th title defence - with Chris Eubank's record of 15 super-middleweight defences in his sights - and another win could secure a mouth-watering clash with middleweight king Bernard Hopkins.

"Calzaghe has made a big mistake by taking this fight," Jimenez said. "He thinks that I will be under-prepared because it is just over two weeks until the fight.

"If he is thinking that then he couldn't be more wrong. I'm fit and ready and will give him the shock of his life on the night."

With the Calzaghe camp already making plans for a lucrative showdown with Hopkins, Jimenez - beaten only once in 22 fights - believes he is not being taken seriously by the Newbridge fighter.

"All I have heard him talk about is a fight with Hopkins, so it seems to me that he is looking past this title defence - a classic mistake to make," Jimenez added.

"I will take his title, unbeaten record and end his hopes of a Hopkins fight."

But Jimenez clearly has respect for Calzaghe's abilities as the Puerto Rican revealed he has been working towards this opportunity since turning professional.

"I chose the WBO route [to a world title] because I wanted a fight with Calzaghe - that was always the aim.

"No question, he is the best out there, which is why victory will be all the sweeter.

"My opportunity against Calzaghe has come sooner than expected but I am fit and prepared; I have nothing to lose and everything to gain."