All four Premier League teams failed to win the first leg of their last-16 Champions League ties with Chelsea the only side to register a goal.
"It is one game and they are very difficult opponents," Wenger said. "I think you have first to realise that all four teams came out of the group stage. That means that the level is there.
"After only one game, you cannot judge a general trend. Man City played with 10 men, Arsenal played with 10 men, Man City played against Barcelona, Arsenal played against Bayern Munich, who are world champions.
"Of course you know that with 10 men it will be a difficult game. After that the other two teams are still in positions, Man United and Chelsea, where they can turn the results around.
"Let's wait until the end of the second game before talking about a trend of strength or weakness."
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