Mane received the straight red for a challenge on City ‘keeper Ederson in Saturday’s 5-0 loss, but Liverpool decided on Monday to appeal the three-match ban.
An appeal took place on Tuesday, with the Football Association deciding to uphold Mane’s three-match ban.
It means that Mane will miss the Premier League game against Burnley at Anfield on Saturday, as well as away clashes with Leicester City in the League Cup (September 19) and the league (September 23).
“I don’t think that is a red card. His eyes are on the ball, it’s ridiculous,” Gary Neville told Sky Sports.
“If he wins that challenge, the goal is there for him. It wasn’t one of those where you think the goalkeeper is the favourite.”
Ex-Liverpool centre-back Jamie Carragher took a different view, saying “he had his eyes on the ball, but that doesn’t mean he isn’t endangering an opponent.”
“Jurgen Klopp is right, it is unlucky, and there is nothing sinister from Mane who is only thinking about scoring a goal,” he explained.
“But you have to look at it from the referee’s perspective. What does the rulebook say? In the referee’s book is ‘endangering an opponent’.”
The timing of Mane’s absence could be worse, with the winger still available for Wednesday night’s clash with Sevilla in the Champions League.
With Philippe Coutinho returning from injury, the Brazilian can provide an excellent alternative on the left flank, while Klopp was likely to rotate against the Foxes either way.
Mane can be expected to come straight back into the fold for the trip to Spartak Moscow on September 26.