Walker says Parker has made big improvements since he was in the same New Zealand team at the Delhi Commonwealth Games alongside two of his fighters.
"It is because he is getting top quality sparring, strength conditioning and nutrition, which he was probably lacking as an amateur, and it pays dividends. His total focus in the States will be boxing," said Walker.
Papatoetoe-raised Parker was on his first visit to Tauranga yesterday to promote his upcoming fight against "King Arthur" Afa Tatupu for the NZ National Boxing Federation heavyweight title in Auckland on October 10.
Parker's last fight at home was in June when he knocked out the highly-respected South African Francois Botha in an impressive performance that reverberated around the boxing world.
Parker admitted Botha's trash talking before the fight, when he continually referred to him as "baby Joseph", impacted on his approach to the fight.
"Yeah, I did take notice of it when it is coming straight towards me but I just let him say what he wanted to say," Parker said. "It makes me train harder so I can show what I am capable of doing in the ring.
"Out of that fight it shows everything we have been learning and practising in the gym for me and Kev (Barry) in Vegas is paying off. We are heading the right way and doing the right things and I am feeling a lot fitter and stronger now.
"There were a lot of things I was doing wrong training in New Zealand but now I am open to sparring partners who used to be world champions. I wouldn't get that here."