Victor Valdes has insisted that Barcelona must be at their best to ensure progression into the quarter-finals of the Champions League at the expense of Manchester City.
The two sides meet in the second leg of their last-16 clash on Wednesday, with Barca holding a 2-0 lead from the first leg in Manchester last month.
"Some might think City ceded the ball to us, but I look at it as Barcelona playing well," he told The Guardian.
"I don't think the tie's over - 2-0 is a good result but not definitive, especially with the talent they have. And [Sergio] Aguero will be back.
"He scored goals against me at Atletico and he's a spectacular player: he gets shots away quickly and moves intelligently. They're a great team. We have to play well or it'll cost us."
Valdes will leave the Camp Nou on a free transfer at the end of the season.
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