Wales had targeted at least three wins from their four Dove Men Series matches but only managed victories over Argentina and Tonga.
Faletau admits it is disappointing, none more so than Saturday’s 30-26 defeat to Australia – the Wallabies ninth straight victory over Wales.
“It is frustrating because we have played Australia so many times and just lost,” said Faletau.
“We have not beaten any of the big three but we just have to go back and look at the game and see what happens when we come up against them again.
“It was a tough game, one of the hardest against Australia. We made a really good start to build a lead but we allowed them back into the match.
“Australia have a really good backline and you could just see what they did out there. They can strike from anywhere.
“It was a disappointing autumn because we set ourselves a target of three wins and we have not managed that.
“A few boys have come in and done well and we have to look forward now and concentrate on the Six Nations.”
No side has won three outright titles in a row in 130 years of Championship history.
Sam Warburton challenged his side to write history in 2014 and Faletau admits it is a major motivation.
“We have to look ahead to what is in front of us and try to defend our title,” added the Newport Gwent Dragons star.
“I don’t think there has been a team to win three Six Nations titles in a row, and that is what we have to target. That is a motivation as we try to make history, so if you can’t get up for that then you shouldn’t be playing.”
