#1 Cillessen too good to be a back-up
Ever since arriving at the Camp Nou, Cillessen has been playing the role back-up keeper behind the German international, Marc-Andre ter Stegen, who has been performing at very high levels for Barca. But the performances of Cillessen over the past 2 years prove that he is too good to be a back-up.
Although one may argue he isn't at the level of Oblak, De Gea, or Ter Stegen, he surely can improve any team in need of a good goalkeeper. In the quarter-final against Sevilla, he made many crucial saves, but the most important of all was a penalty he saved early on which could've sent the match either way, and was very crucial for Barcelona's victory in the game.
It may seem like Cillessen is happy to be playing the role of a back-up, and it may be the best goalkeeper pairing ever, with a quality back-up available for Ter Stegen on the sidelines.