The two rivals will lock horns once again on August 20 in Saudi Arabia, with Joshua looking to avenge his defeat to Usyk in London last September.
Watford's Joshua was comfortably outboxed over 12 rounds and suffered a second defeat of his professional career, losing via a unanimous decision.
At 6ft 6ins, Joshua has a clear height advantage over 6ft 3ins Usyk, and pundit Nelson told Sky Sports: "This is not an impossible task. It's very possible. AJ's got to go in there with the right mindset, the right game plan.
"This is a fight he can win and become a three-time heavyweight champion of the world.
"Look at the last fight. Look at the state of Usyk when he came out. Usyk looked like he'd been hit by a bus even though he won and AJ lost.
"AJ now has to go in and do what he does. Go in and fight his fight. So let's see if there's a difference. Use that height, use that range. Use that ruggedness about him.
"If he uses that, I cannot see him losing. Yes, the hullabaloo is there about Oleksandr Usyk but he is beatable. It can be done."
Joshua is also being backed to secure victory by rising cruiserweight star Richard Riakporhe, who trained with him before Joshua jetted to Saudi Arabia for a training camp.
"I can't give away the game plan because I would get slaughtered but one thing I will tell you, the intensity, the intention behind his shots when he throws, the hunger, with what he's achieved so far, coming back into the gym day in and day out," Riakporhe told Sky Sports.
"A lot of people would not be able to do that if they had achieved what Anthony Joshua has achieved so far. He's hungry. He wants to create a legacy for himself. "