After a quarter of a century away from European football, the prospect of modest Spanish side Rayo Vallecano making their first ever final must rank as one of the season's bigger surprises. They may be midtable in La Liga but humble Rayo, from the working class neighbourhood of Vallecas in the southeast of the Spanish capital, are a far cry from their illustrious neighbours Real Madrid and Atletico: they are usually more concerned with survival than European finals.