:thup:, Hawshiels, good stuff there.
To the OP - knockout tournaments are notoriously tricky. Luck plays a
huge part, and as any fan of the F.A. Cup will tell you, the best team is not guaranteed to win in any given match. Since, to win a knockout tournament, you have to win a number of matches in a row, and only one team can do so .. well, the other 31 are going to go home on a loss.
As Hawshiels says, facing a top team in the C.L. is a lot different from facing a mid-table team in a league match. Its not just your tactics you might want to look at - its your squad selection, your team-talks, your media usage, everything.
In the biggest matches, the mental attributes play a huge role - if your dream-team is built in the "Physical and Technical" world, maybe your team just doesn't have the mental discipline to win on the biggest stage?
Experience is key. Determination is crucial. Decisions are critical. Concentration and Composure, definitely. The hidden "Important Matches" rating is going to play a huge role.