The 28-year-old suffered a miserable campaign last season - making just three appearances, all of them in the Capital One Cup - as he lost his place in the Republic of Ireland national side.
He started the friendly in Serbia in August last year before playing in the World Cup qualifiers against Kazakhstan, Germany and the Faroe Islands, but then lost his place as Giovanni Trapattoni decided he needed his first-choice goalkeeper to be playing regular football.
Having suggested he may have to leave the Stadium of Light to find that regular starting place, he may find himself with another chance should Simon Mignolet complete his expected move to Liverpool.
"I love it at Sunderland, but if I'm not going to play... It's a tough decision, but I need to play football, I think that's evident in itself," he said.
"A lot of stuff can happen over the off-season. Basically, I just want to play football.
"I'm looking forward to the future, if I'm honest. It's been a frustrating 12 months or so, so I'm looking to come out of the dark times and into some good ones."