The former Chelsea centre-back is full of respect for the Catalan powerhouse, and expects a difficult match in the French capital
The Parisiens are preparing for the first leg of their Champions League quarter-final against the Blaugrana, and Alex realises they face a tough task to emerge victorious at the Parc des Princes.
"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.