Tim Krul
Perhaps a surprise name in the list having barely played for a couple of years after disappointing loan spell with AZ Alkmaar and Brighton, the 30-year-old retains a good reputation in Europe and at the age of 30, has plenty of Premier League experience under his belt. A team-mate of Cillessen's at international level, Krul's kicking has often been described as suspect, something which could put Barca off given their propensity for playing out from the badk.
Rui Patricio
Having spent his entire career to date with Sporting, it appears the experienced stopper's time at the club is coming to an end. With almost 500 professional games under his belt, the 30-year-old has proven himself as one of Europe's best, but his self-confidence means that he isn't likely to accept being second choice to anyone.
Joel Robles
The former Spain youth international has carved out a niche for himself as a second-choice goalkeeper, having failed to reach his century of top-flight appearances despite making his debut almost a decade ago. The 27-year-old knows all about La Liga, having come through the academy at Atletico Madrid and could now be set for a return to his homeland.
Vicente Guaita
Whilst it appears that Guaita will be heading for Selhurst Park to join Crystal Palace this summer, a phone call from Barcelona could potentially still change that. The 31-year-old has developed significantly since leaving Valencia for Getafe four years ago and it widely considered one of the best stoppers in Spain.