German legend Rudi Voller admits the Premiership is the strongest competition in the world.

The Bayer Leverkusen sports director told Setanta Ireland: "It's no coincidence that all four English teams - Manchester United, Liverpool, Arsenal and Chelsea - are in the quarter finals.

"They've even overtaken the Italian clubs in regard to the financial resources available and that's why it will be difficult to get past these four teams in the future."