Arsene Wenger must start learning from his mistakes if Arsenal are to compete at the highest level of European football, Alisher Usmanov, the London club's second-largest shareholder, has said.
The Russian billionaire, who owns 30 percent of the Gunners, is frustrated by Arsenal's worst start to a Premier League season which has brought four wins from their first 12 matches.
"Arsenal is a dream that sometimes becomes a mirage and sometimes a pain," Usmanov was quoted as saying in British media on Tuesday ahead of the club's midweek Champions League clash at home to Borussia Dortmund.
"The potential of the team is there, but there is no critical evaluation of mistakes.
"No genius can retain the same level of genius if they do not acknowledge mistakes. We just repeat the same mistakes year by year."
'When we go through a difficult patch, we show solidarity'
Arsenal ended a near decade long wait for silverware last season with an FA Cup triumph but the optimism that instilled has faded quickly.
Consecutive league defeats to Swansea City and Manchester United have left Arsenal in eighth place. They also lost early in the League Cup and recently threw away a 3-0 home lead in the Champions League against Anderlecht to draw 3-3.
Wenger has been heavily criticised for his tactics by the likes of former midfielder Paul Merson, but he responded to the latest attack by Usmanov on Tuesday.
"In the 18 years I have been here I have shown that I can take criticism," he said.
"Everybody has the right to have an opinion. Having said that, we have values at this club.
"The first one is when we go through a difficult patch, we show solidarity. That is a very important one. The second one is that, when you have something to say to each other, we say it face to face. We don't need to go to the newspapers."
'Restrictions are always lost possibilities'
Arsenal should qualify for the knockout rounds of the Champions League but defeat by Dortmund on Wednesday could leave them vulnerable.
Arsenal's lack of defensive stability has been held up as the team's main failing of the season so far but Usmanov believes all departments need strengthening.
"We need to strengthen every position to play on the level of such teams as Chelsea and Manchester City and in Europe like Real Madrid, Barcelona, Paris St Germain and other clubs," he said.
"I like Arsene for his principles," he added. "But principles are sort of a restriction. And restrictions are always lost possibilities."