An independent tribunal determined that Matosevic committed five anti-doping rule violations between 2018 and 2020, including use of a prohibited method through blood doping and facilitating another player to blood dope, providing advice to others on how to avoid positive tests, and use and possession of the prohibited substance clenbuterol.
Matosevic denied all charges throughout the process, until admitting to blood doping in a social media post shortly before the hearing was scheduled to take place.
The 40-year-old - who reached a career-high No.39 in the world in 2013 before turning to coaching - was highly critical of the ITIA's investigative practices.
He said he was in Mexico when he "stupidly" received a blood transfusion in 2018, before retiring shortly afterwards, partly, he said, out of disgust at his actions.
"I am writing this confession letter firstly to warn other athletes against doing anything that may harm their health and put their lives at risk, because there is a long life after an athlete's career," Matosevic said in a statement released to Australian tennis website The First Serve last month.
"Secondly, I am writing this letter to let the tennis world know how corrupt and unjust the ITIA process is.
"They take your phone number under threatening circumstances and make legal cases over photos and text message assumptions that are literally 5 years old.
"The whole process is corrupt and lacks credibility, as we have seen over the last few years!''Â
The tribunal dismissed Matosevic's allegations as without merit, and said the ITIA "acted within the authority conferred" by the Tennis Anti-Doping Protocol (TADP).
On the charges relating to advising other players, independent tribunal chair Michael Heron KC said Matosevic's actions "went far beyond passive association and constitute intentional participation" in violation of the TADP, and that his "conduct strikes at the integrity of the anti-doping framework".
Since retiring in 2018, Matosevic has coached fellow Australians Chris O'Connell and Jordan Thompson.
