Sinner received a three-month ban agreed with the World Anti-Doping Agency (WADA) in February after “admitting “partial responsibility” for team mistakes.
Ferrara, in his first public remarks on the scandal, laid the blame squarely at the door of Sinner’s former physiotherapist Giacomo Naldi.
Both of them have been laid off by the 23-year-old since the affair came to light.
WADA came to an agreement with Sinner after accepting he was inadvertently contaminated with the banned substance clostebol by Naldi.
Ferrara told Gazzetta dello Sport that he had used the spray himself for years after it was prescribed by a doctor for an illness.
“I was perfectly aware that it was banned so I always kept it safely stashed away in my wash bag,” he said.
“I suggested Naldi use it for a cut which had not healed and was affecting his work.
“I was absolutely clear when I spoke to him about the nature of the product and it was imperative it never came into contact with Jannik.
“In effect I told him to use it only in my bathroom.
“Naldi did not deny he had been told, but he said he could not recall.”
Ferrara said he did not know Naldi had been gloveless and also not washed his hands after using the spray when he treated Sinner, especially after “the warnings he had given him”.
“With hindsight, it is easy to say I would not do things the same way,” he said.
“Of course I am not proud of the behaviour of others.”
“I have suffered during this affair owing to the bad faith of some,” added Ferrara, who has since joined the entourage of 2021 Wimbledon finalist Matteo Berrettini.
Sinner’s suspension ends on May 4, allowing him to return in time for the French Open, the second Grand Slam event of the year.
The clay-court tournament in Hamburg will be Sinner’s second tournament after his return as he will also compete on home soil at the Italian Open in Rome from May 7-18.
The reigning US and Australian Open champion Sinner reached the French Open semi-finals last year.
This year’s tournament is scheduled to run from May 25 until June 8. (AFP)
