Torres struck the only goal of the game for the 1-0 win.
Xavi said, “We faced a good deal of adversity during this match, even though our first half was pretty good.
"This is the Champions League. FC Porto is a big club in European football. We suffered, but I'm happy with the way my team worked. We sacrificed ourselves, we fought and we left our soul in the field to take the three points, which were vital.
"As for the second half we really needed to control it more. Champions League matches tend to demand a lot more from you if you want to win.
“Lewandowski went off because he took a really strong kick. Lamine had also been warning us for a good few minutes that he felt sick and had a sore stomach. We took him off because he couldn't continue any more.
“Araújo only has cramps - let's see how many of them we get back for the weekend. As for me and my booking that's how I 'live' matches.. That's all gone well for me across my career and it's difficult to change now."