Lee Purdy insists Devon Alexander is not an 'elite' fighter and he plans to dethrone the IBF welterweight champion on Saturday night.

Purdy stepped in to face Alexander on short notice after Kell Brook's withdrawal through injury and he is a major underdog ahead of their world title clash in Atlantic City.

The former British champion has halted his last four opponents, but he is making a big step-up in class against Alexander, a two-weight world champion with just a solitary defeat.

Alexander has been touted as a possible foe for Floyd Mayweather or Amir Khan, but Purdy is far from overawed by the American and does not think he is one of the sport's top performers.

He told the Ringside Toe 2 Toe podcast: "I've fought the fight over 100 times in my head already, but I'm just going to go there and do what I do and put on a good performance.

"I believe I've got a really good chance. I'm really strong, I punch really hard, I take a good shot and you know Devon is a good fighter, but he's not one of the elite fighters."

The Essex man knows he cannot outbox the slick southpaw and must drag Alexander into a dogfight if he is going to create a huge upset.

"A lot of people are writing me off, but I've got no pressure on me. I'm going to go over there and do what I do," he said.

"If everyone knew the script, no-one would watch boxing. That's why I'm here to put on a great performance and do the country proud.

"I've never lost to a southpaw. I think I've knocked my last three or four out.

"Of course I'm going to pressure him. I'm not going to sit on my back foot and outbox Devon, but as long as he doesn't hold me, it will make for a good fight.

Trainer Tony Sims has warned against writing off Purdy as he feels 'Lights Out' is capable of producing a knockout with his punch power.

"That's the thing about boxing, you never know. The underdog has always got a chance, especially when he's a puncher," said Sims.

"Lee Purdy always has a chance of winning any fight because he can punch with either hand and if he catches you, he can put you out."