Campbell, who worked with Torres towards the end of the 2010-11 season, insisted the striker just needed a period of fine-tuning to regain his speed and confidence.
"It's something best done in pre-season but Fernando just needs two weeks when he hasn't got to worry about playing on the Saturday," Campbell told the Daily Telegraph.
"Just put in a nice two-week training programme that I think would definitely bring the majority of his speed back.
"I'm sure I could fix him," added Campbell, who won a relay gold medal at the 2004 Athens Olympics and now works as a sprint coach in football and rugby union.
"It doesn't have to be a lengthy process because these guys are already extremely fit. You're not having to worry about the base fitness so you just go in and teach the raw speed."
"Fernando had real pace," said Benitez. "You have to work in the gym on strength. Maybe he needs to do that again."
Torres has suffered a crisis in confidence since his record £50 million switch to London two years ago, scoring just 11 league goals.
Campbell suggested Torres should bulk up a little to help improve his power.
"In the case of Fernando, I think he would also probably need to do a bit of weightlifting as well as the running and the speed drills to put some power back into his muscles," he said.
"That's why sprinters lift weights, to gain that explosive speed and power."
"I only did about two or three sessions with Fernando but I could see his confidence coming back," Campbell said.
"The biggest problem is that when you lose your speed you're unable to do what you used to be able to do. So then you start trying harder and harder. But that can be counterproductive.
"If you want to be quick, there's an element of relaxation that's involved. You've only got to look at Gareth Bale. He runs at high speed but it's all relaxed and there's no tension in him.
"The problem with someone like Fernando Torres is that the harder he tries to find that speed, his efforts are actually detrimental."
Campbell traced Torres's problems to his injury-hit 2010 World Cup and highlighted two instances from the recent 0-0 draw with Manchester City to outline the extent of his troubles.
"Kompany we know is very quick but Milner is not exactly lightning by any stretch of the imagination.
"A striker without any natural speed wouldn't have knocked the ball out of his legs to chase after. It shows he is playing as if he still believes he has the speed but he clearly hasn't.
"A sprint coach could help him," he added. "I'm 100 per cent sure of that. I believe that if you can put the speed back into his legs then, boy, you will see a very different and far more confident Fernando Torres."