Duff was part of the side which lost Saturday's home leg by a 1-0 scoreline at Croke Park.
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But despite falling behind in the tie to Nicolas Anelka's deflected second-half goal and being written off by some media critics, Duff is bullish ahead of Wednesday's second leg in Paris.
"We've taken an awful lot of positives out of Saturday," he declared. "Other people may not have but we think we can go there and do it.
"We just have to go there and enjoy it. We still think we can do it, so bring it on.
"We have obviously given ourselves an uphill task. Away goals are a massive thing in football but, if we go over there and nick one, it is game on again.
"We are all confident we can go and do it. You have to be."
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