The Spanish champions got up and running in this year's competition courtesy of Arda Turan's late strike, extending their impressive home record.
Diego Simeone's men avoided defeat in European action at the Vicente Calderon last season and inflicted Juve's first defeat of the campaign on Wednesday.
However, the experienced Juanfran, who supplied the assist for Turan's goal, has warned there is still room for improvement after a scrappy contest.
"It was a very passionate game against one of the best teams in Europe. We played really well and we deserved the victory," he explained.
"Juve are a great team. We still have a lot of work to do; we still haven't achieved anything yet.
"Before the game we said that Juventus were a great team. Their plan was to play long balls and our plan was the same as always: to work hard and keep working hard all game.
"The fact we didn't concede any goals says a lot about our team."
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