Brook was given the toughest test of his career by durable American Carson Jones in July, overcoming a late scare to win a narrow points decision.
Argentine slugger Saldivia stands between Brook and a shot at the IBF title this weekend as the pair clash in a final eliminator in his native Sheffield.
Brook has insisted that he is in peak physical condition after hiring a nutritionist and making adjustments in training to avoid a repeat of his struggles against Jones.
He said: "I hadn't had a good training camp and was struggling with my weight before the Jones fight so I tired towards the end.
"But I've got a nutritionist on my team now who has got me eating all the right things to help me get fighting fit, including stuff like steak and broccoli for breakfast, which is a bit weird at first but I've noticed that I've been flying in the gym and I'm more than ready to knock out Saldivia.
"It was a wake-up call, I make no excuses for that and I can assure everyone that you'll see the new Kell Brook in there on Saturday, even I don't know how good I am going to be."