Best way to design tournament database I'm creating a webpage for placing bets on all matches of the upcoming Euro 2012 football tournament. Need some help deciding what approach to take for the knockout phase.

I have created a mockup below, which i'm pretty satisfied with when it comes to storing the results of all "known" group stage matches. This design makes it very easy to check if a user has placed a correct bet or not. 

But what is the best way to store the quarter and semi finals? Those matches depend on the outcome in the group stage.

One approach I thought of was adding ALL matches to the matches table, but assign different variables or identifiers to the home/away teams for the matches in the knockout phase. And then have some other table with those identifiers mapped to teams... This could work, but does not feel right.
I think that using the team ID is the right way to go.  Another level of abstraction for all of the finals rounds just adds unnecessary complexity for not much benefit other than pre-loading the matches table with data.

The data structure looks pretty solid to support this.  The quarter and semi finals would need to be added to the matches table once the initial match results are in.  If the matches are assigned randomly then this is a manual operation, however, if they are in a particular order...

   A
match 1 -----+
   B         A
          match 5 -----+
   C         C         |
match 2 -----+         |
   D                   A
                    match 7
   E                   F
match 3 -----+         |
   F         F         |
          match 6 -----+
   G         G
match 4 -----+
   H


...then this could possibly be done with a query.  Again, the complexity of the query may not be worth the effort depending on the number of teams