However the 32-year-old has denied he is past his best and believes he still has a lot more to offer the national team in the future.
"I have always felt my best game is my next game or in the future, and I still feel that way," Gregan told The Courier-Mail newspaper.
The scrum-half also believes the high expectations of the Australian press and public has been the catalyst for the criticism of his team.
He added: "It's irrational, especially in today's world of professional sport. On any given day there's one bad call, one poor decision, one not converted opportunity, and you lose the game narrowly. That's the difference."
Gregan's captaincy and place in the team has been questioned since the run of losses on the tour, but it is something he says he is used to.
"There's nonsense (in the press) all the time. I've had nonsense right from the start of my career. There's always been nonsense," he said.
"It just intensifies a bit more when you're captain of the national team and the team is not performing, results-wise."
Gregan had shied away from the media spotlight since returning home from the tour which brought about the demise of former national coach Eddie Jones.
However, he admits the wave of new faces in the Wallabies line-up, as a result of injuries to senior players, was a major contributor to the poor results on tour.
"The reality of the team at the moment is that we've had about 15 new caps this year and we had a ridiculous injury toll even before the season started," Gregan said.
"We're playing and losing Test matches narrowly but it's all good experience for the guys long-term, and they'll be better players for it."