The 34-year-old all rounder will take on American Richard Dawson at the MEN Arena in Manchester on Friday after exchanging his cricketing whites for a pair of boxing gloves in a bid to prove himself in the ring.
Flintoff, who was part of England's Ashes-winning teams in 2005 and 2009, tipped the scales at 216lbs (97.98kg), 25lbs (11.34kg) lighter than his 23-year-old opponent who already has two professional victories.
“I'd be lying if I said there weren't a few nerves but I've been nervous before playing cricket and used it to my advantage,” Flintoff told Sky Sports News.
“There will be critics and doubters out there and it's a big task I've taken on. I'm just concentrating on the fight and we'll see what the reaction is.
“It depends if you take it on board, as a cricketer I didn't read too much of the press, I just wanted to be comfortable in what I'm doing.
“It's not something we're talking about in our camp, we're concentrating on tomorrow night and putting all the good work into practice.”
Dawson said: “This is my job. It's a hobby for him. He's taking food from my family.”