Joseph Parker's trainer said the WBO heavyweight champion is a "different animal" after undergoing surgery on both elbows ahead of his fight with Anthony Joshua.
Parker had been in pain for the last two years, but the New Zealander went under knife before Christmas to resolve the issues that were hampering him.
Kevin Barry said the unbeaten 26-year-old will be firing on all cylinders when he steps into the ring for a unification bout with Joshua in Cardiff a week on Saturday.
"We have not been hiding this but now it has come out I can tell Joshua that Joe will be a different animal from the one he saw taken the distance by Hughie Fury." said Parker's trainer.
"There were chips of bone floating in both joints, stress in the sockets and severe calcification of the bones in those areas. Joseph has been in such pain that we had to limit his training sessions, especially his punching.
"Without question this had a big effect on his performances in 2017. By the time he came over here to fight [Hughie] Fury he couldn't straighten his left arm. So he couldn't lead with his jab as normal and had to rely on just throwing left hooks.
"We have not been secretive. All the media who came to our sunshine training camp in Las Vegas will have seen the scars on both elbows.
"So successful has the surgery been that Joe is happier than for a long time. He is pain-free and in much better condition.
"Because he can train normally, he is leaner and with a glow on him, as people have noticed since he's arrived in London."