Keeper Mark Schwarzer, a key figure in Fulham's run to the final, told BBC Radio 5 Live that the team believe they can still go one step further and beat Atletico in the final.
Boyce and Scharner played key roles in last season's successful battle against relegation, while Mike Pollitt provided back-up to keeper Chris Kirkland.
After a low-key opening Wales took the lead in the 23rd minute, with Koumas sending a well-directed header beyond Irish keeper Shay Given after Joe Ledley had beaten Steve Finnan to deliver an inviting cross from the left flank.