Quote: nottinghamtiger "History suggests otherwise. Very few teams who play at Wembley win the grand final.'"
Since the first Grand Final in 1998, there's been 12 Wembley finals, of which 5 eventual Grand Final Winners have been present. If we include the non-Wembley finals in that (2000-2006) then 9 of 19 Grand Final winners have played in the Cup final the same year.
Breaking it down further and looking at how each Grand Final Winner has done in the Cup:
Cup Winners - 4
Cup Runners Up - 5
Cup Semi - 2
Cup Quarter Final - 1
Cup Round of 16 - 6
Cup Round 4 - 1
So Cas losing in the Quarter Finals isn't looking promising for you really....