@[deleted] Yes, the Sagan thing.
The chance will vary from year to year, but if a club regularly qualifies for the semi-final, then it must (almost by definition) be a strong club and have a non-negligible chance of overall success (somewhere around 10% to start, perhaps).
Since 03-04, Chelsea have finished as semi-finalists or better six times which if their chance of going on to win from a semi is, cautiously, 10% gives them an 50% chance of having won it at least once. Which they now have.
During that time, they've had considerable continuity in their squad which we have sadly lacked.
We've only made the semi-final or better twice in the same period. But if we do start to consistently get there we will eventually take the victory. We came so close in 06, a tragedy at the time and even moreso in retrospect.
