Conrath is Bachelor of Science in exercise and health and is currently studying masters in Gold Coast, Australia.
John was with the team in the London Olympics in which India finished 12th after failing to win a single match.
It has been learnt that John was hired on a monthly salary of USD 5500 by the Sports Authority of India last year on the recommendation of coach Michael Nobbs. There had been a significant change in the fitness level of players after his arrival. There were reports of his coming back after Nobbs joined the camp in Patiala last week.
However, Hockey India's secretary general Narinder Batra has confirmed that John will not come back.
"John has refused to come, so we have appointed another Australian Jason Conrath as the new trainer for the team," he said.
"We have sent him the contract yesterday and after receiving that he will apply for the visa. I hope that he will join the team before 15th November."
Batra also said that it was Nobbs who had suggested Conrath's name to HI.
"It is only after coach's recommendations any support staff is appointed. Nobbs has suggested Conrath's name and we found him eligible for the job."
India will take part in the Lanco International Super Series at Perth from November 22 to 25, which will also feature England, Australia and Pakistan.
The Lanco Series will be followed by the FIH Champions Trophy at the State Netball Hockey Centre in Melbourne from December 1 to 9. India are placed in Pool A alongside England, Germany and New Zealand, while hosts Australia, Belgium, Netherlands and Pakistan are in Pool B.