Neuer has been first choice at Bayern when fit but is said to be considering a move away from the Allianz Arena, citing what he perceives to be a lack of ambition shown by the German giant in the transfer market.
The player’s agent, Thomas Kroth, told Suddeutsche Zeitung that Bayern have fallen too far behind their major European rival and the 33-year-old may have to join a new team if he is to win the UEFA Champions League for a second time in his career.
"He wants to win Euro 2020 and he wants to win the Champions League again," Kroth said.
"Manuel is success-oriented. My impression is that the gap to the top four English top teams is already serious and the Munich squad is currently not yet as competitive or set up to tackle Manuel's goals seriously.
"When he realises that Bayern are responding, then he will probably blossom again."
But those comments have not gone down well with club legend Matthaus, who feels the Bayern skipper should have discussed the matter privately rather than let his representative speak to the media.
"His behaviour is totally unacceptable," Matthaus told Bild. "As the captain of Bayern he should speak to the club if he has a problem with the situation over signings.
"The doors of the management are always open.
"I know his agent - he's someone who doesn't usually show up in public of his own free will. Manuel will have agreed with him. My representatives would not have been able to express themselves in this way without my consent."