"If you look at the teams we could be paired with I think they all present a difficult challenge," said the Basque.
"Italian teams are always tough to play against, while Olympique Lyonnais and Bayer Leverkusen are great teams as well. Because of this we can't worry about who we draw.
"I think we can go far in the Champions League this season but we have to take each round as it comes.
"It was very important for us to get into the last 16 but we know we'll have to improve and play well to progress past this stage and beyond. It is going to be difficult be we are confident."