Around 20,000 Rangers fans will be in the Estadio Ramón Sánchez-Pizjuán to cheer on their side in the Europa League final.
Club bosses believe half the fans in the 40,000 seater stadium will be Light Blues fans - after diehards more than doubled the number of tickets handed to the club.
Only 9,500 tickets were given to the Ibrox side for the showpiece clash with Eintracht Frankfurt by UEFA.