Barnes believes that Mane is inseparable from Jurgen Klopp's decisions, despite his efforts for end product over recent weeks.
He had many prolific presences for Reds during his time at Liverpool.
He scored 88 goals in 193 appearances and with his efforts, he helped Liverpool win the Champions League, the UEFA Super Cup, the FIFA Club World Cup, and the Premier League.
However, Mane has only scored two times in his 13 recent games and three times in 18 outings.
He is not the first player to face this situation, with Roberto Firmino seeing his value called into question when going through a barren run, but Barnes sees no reason to warn at Anfield.
Barnes said: "This is very much the same thing we talked about last year with Firmino, where we won the league by 20 points, yet people were complaining that he wasn't scoring enough goals. Yet, he was playing every game and contributing to the team's overall performance.
"Firstly, it's important to remember that Mane has been one of the most important players in the team and his form is excellent. Perhaps not excellent in terms of number of goals scored, but excellent in terms of what he does for the team. I'd even say that Mane has a lot to do with why we're at the top of the league, and that's done both on and off the ball.
"His goalscoring, his creativity - it's a package deal. So I don't see why it's all doom and gloom for a team that's top of the league.
"And yes, the last two games haven't gone our way, but that could easily be turned around, and I expect them to do so.
"So I don't think it's fair on anyone in that team to start complaining and saying that the players are under-performing when this is exactly what happens in football. You win some, and you lose some - simple as that.
"But Liverpool is a fantastic team, and the way they play shouldn't be criticized nor scrutinized. Like any team, you'll have good days and not so great days - but it all comes down to consistency, and that is something that this team has proven to be."