The midfielder, who has played for both clubs, believes Tito Vilanova's team will be too strong on home soil, but the result may be different in the return fixture in Scotland
The 24-year-old, who now plays for Mexican outfit Santos Laguna, came through the ranks with the Catalan giants before moving to Glasgow for a three-year spell between 2008-2011.
Crosas believes that the Scottish champions will have to try and soak up a lot of pressure from the home side and utilise their dangerous forward players if they are to take anything from the Group G encounter.
"I think at the Camp Nou they will be more closed and try to surprise on the counter," he told Mundo Deportivo.
"They can do damage with men like [Gary] Hooper or [Giorgios] Samaras, who are decisive strikers and always appear in the important moments."
Despite being massive underdogs, Crosas believes that Neil Lennon's team could cause an upset in the return fixture at Celtic Park because of the electric atmosphere created by the fans.
"In Scotland it will be different as Celtic will have more tactical options.
"If Celtic want to qualify for the next round they should take maximum points at home. And they are well aware of that.
"They will also be boosted by the atmosphere that will live in the stadium. It is very difficult to explain."
The former Spain Under-21 man refused to be drawn on who he would be cheering for during the match, though he admitted that he would be pleased for which ever side came out on top.
He added: "Being born in Barcelona and having much love for Celtic, I always want both clubs to win. I expect a victory from Barcelona to leave the qualification on track.
"Still, I must admit that is the first and only time in history that if my team loses I will be happy."