O'Brien, who was drafted to the club at the end of 2011 and made his debut in 2012, said he had no qualms about being part of the contentious supplements program when he joined the Bombers.
"Not for one minute did I hear, think or feel I was part of a program that was going to be seen as illegal," O'Brien told The Ballarat Courier.
"I just assumed that's what happens at AFL footy clubs. I just couldn't wait to get into it (training); you just want to be a part of it when you’re new."
O'Brien's two-year contract with the club ended after this season but the midfielder has hopes of signing another deal with the Bombers.
He offered his support to suspended coach James Hird and Dr Bruce Reid, who was also charged by the AFL.
"I'm really keen to help the club wherever I can," O'Brien said.
"I'm not overly concerned about my long-term health at the moment.
“I trust Dr Bruce Reid with my life and I’ve sat down with him and talked about everything.
"My family has been great as well. Mum and Dad have supported me the whole way.
"It’s not easy for them when their son is in Melbourne and part of one of the biggest-ever sport stories in Australia."
Reid has taken his fight with the AFL to the courts, but Hird was banned from coaching for 12 months as part of the penalty handed to the Bombers.
They were also kicked out of the finals, fined $2 million and stripped of draft selections.
O'Brien praised Hird for his strength during the scandal.
"James (Hird) was unbelievable in the way he handled it," O'Brien said.
"I'm not putting him up on a pedestal and saying everything he did was the right thing, but the way he supported and defended us as players was fantastic."
Twitter: @AFL_CalTwomey
