The former Chelsea centre-back is full of respect for the Catalan powerhouse, and expects a difficult match in the French capitalParis Saint-Germain defender Alex feels Barcelona are the best team in the world, and added that every footballer dreams of playing for the current Liga leaders.
"For me, Barcelona are the best team I have ever seen play. Every footballer wants to play at Barcelona and be a part of that team," the Brazilian defender told Onda Cero.
"However, they are not unbeatable, We must put in a good performance. We have to play like AC Milan did in the first leg at San Siro. Barcelona tend to struggle against teams that play on the counter-attack.
"[Lionel] Messi and [Andres] Iniesta are their two main dangermen. We need to pay them close attention. With a bit of luck, we can get a good result."
Tuesday's match in Paris is scheduled to kick off at 20:45CET.