Arsenal's second largest shareholder Alisher Usmanov has told Arsene Wenger to start learning from his mistakes and claims the Gunners need to strengthen the entire team to compete with the best in Europe.
The Russian billionaire, who owns 30 per cent of the club, was keen to emphasise his admiration for Wenger but believes the Frenchman is letting his principles stand in the way of Arsenal's success.
The Gunners have lifted just one trophy in nine-and-a-half years and a 2-0 defeat at home to Manchester United on Sunday marked the team's worst start to a season since 1982.
Usmanov told CNBC: "Arsene Wenger is one of the greatest coaches, not just of European, but of world football.
"But we have a Russian proverb which goes, 'Even an old lady can have a roof falling on her'.
"Everybody makes mistakes. He can make mistakes and I know as you age it is more difficult, more challenging to accept one's mistakes."
Usmanov continued: "The potential of the team is there but there is no critical evaluation of mistakes and they need to acknowledge them.
"Because no genius can retain the same level of genius if they do not acknowledge mistakes.
"It's only when you admit your mistakes that you can get rid of them. I wish this to my club.
"Nothing bad is happening apart from repeating the same high result - we keep being in the middle of the Champions League but we only lose the first play-off games.
"Some may be happy with that but as a share holder, I am not."
Wenger's position as manager has come under intense scrutiny in recent seasons as the team has drifted further away from a serious challenge in either the Premier League or the Champions League.
Usmanov, who has not been offered a place on the Arsenal board, admits it is "frustrating" to be excluded from discussing the manager's future but suggested he still supports the Frenchman, adding "the club leadership relies on Wenger".
Arsenal spent £35million to sign Alexis Sanchez in the summer, a year after breaking the club's transfer record to buy Mesut Ozil for £42.4million.
Usmanov insists, however, that money is available to add more quality and Wenger must not allow his principles to translate into "lost possibilities".
"Does (Wenger) have money or not? There is officially money in the club," Usmanov said.
"My opinion - and I tell it openly - we need to strengthen every position to play on the level of such teams in [the] UK as Chelsea and Manchester City, in Europe like Real Madrid, Barcelona, Paris St Germain and other clubs."
Arsenal need one point from their two remaining Group D games to qualify for the last 16 for the 15th successive season. Europe's elite club competition will prove a welcome distraction from a beleaguered league campaign -- even if 2013 runners-up Borussia Dortmund represent formidable foes tomorrow.
"Last season we lost at home and won away (to Dortmund), so we hope this season we can turn it around and get a result against them at home," Arsenal goalkeeper Wojciech Szczesny said.
"We have confidence for Wednesday's match knowing that we have recently beaten them. If we put in a good performance at home we know we can win."
It has not been all plain sailing for Arsenal in Europe this season and they squandered the chance to secure passage to the knockout stages once already in their last match at home to Anderlecht.
Wenger's side threw away a three-goal lead to draw 3-3 on that occasion but with seven points from four games they are comfortably-placed in second, five points ahead of Anderlecht and six clear of Galatasaray.