Just under 34,000 spectators turned up for Tuesday night's Group E opener against Bayer Leverkusen, manager Andre Villas-Boas' first European match in charge. The attendance was still 10,000 more than for the group game against Rosenborg four years ago, a fixture that represented a nadir in club-supporter relations over ticket prices. But Tuesday's figure did follow a 33% rise in Champions League ticket prices, which has upset some fans and has sparked a campaign on Twitter for a boycott of next month's home match against Genk. Chelsea Supporters' Group vice-chairman Michelle Shaw wrote on her organisation's website on Sunday: "Not only am I boycotting Genk, I am also boycotting Leverkusen and Valencia. "My choice, I know, but I made the decision as soon as the ticket prices were announced. "Why? Because I don't want to wake up one May and find I can't afford my season ticket any more. "The only way to send a message to the club is by a low attendance at the Genk game." Chelsea slashed their Champions League prices almost in half after fans baulked at paying £48 per ticket for the Rosenborg game. But they went back up to £40 this season, with tickets for other competitions also increasing for the second straight year following a four-year season-ticket price freeze. It is understood Chelsea are remaining calm about last night's attendance figure, part of the reason for which was the short window between the group-stage draw being made and the fixture, with clubs always preferring to play their opening game away to give them longer to sell tickets for their first home match. It remains to be seen how the Blues will respond to a significant boycott of the October 19 Genk game as they attempt to balance the demands of UEFA's new Financial Fair Play regulations with maintaining an expensively-assembled squad and keeping supporters happy - all the time playing in a 42,000-capacity stadium dwarfed in terms of matchday income by Manchester United's 76,000-seater Old Trafford and Arsenal's 60,000 Emirates Stadium.