The Catalan club were slapped with a transfer embargo effective for the next two windows by FIFA last week.
Barca were found to have breached rules in making 10 signings between 2009 and 2013, but have since confirmed their intention to appeal the sanction.
However, Xavi revealed the mood at the club is one of injustice.
"In the dressing room and the club, we believe that the sanction is disproportionate and unfair," he said. "La Masia (home of the youth squad) does everything perfectly correctly and we’ll try to defend it to the maximum.
"We hope that it all comes to nothing."
Barcelona meet Atletico Madrid in the second leg of their UEFA Champions League quarter-final on Wednesday, tied at 1-1 from the first game, and Xavi wants the controversy to inspire Barca to victory.
"We've suffered so many blows this season but we still feel strong and competitive," he added. "These things unite the team."
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