Barca beat Arsenal 2-1 in the 2006 Champions League final, and are in fine form domestically and in Europe, with Lionel Messi on a particular hot streak.
"I believe that we will not be favourite," Wenger said in responce to the draw.
"But for me it will be a 50-50 game and that's how we have to take it.
"They are a good side, we are a good side, it will be an interesting and exciting game over two ties, and we'll make sure that we have the focus and belief right."
However, Wenger was also keen to not look too far beyond Saturday's Premier League clash with West Ham United.
"It's much more important to focus on tomorrow's game against West Ham than it is on the Barcelona draw," he added.
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