The 24-year old Dutch striker has signed a pre-contract agreement to land at Carrow Road in the summer but only if the Norfolk club do not get relegated from England's top flight.
"There is a special clause in the deal accepted by all parties that stipulates if Norwich leave the Premier League then the future of Ricky van Wolfswinkel will be open again," van Wolfswinkel's agent Louis Laros told A Bola.
"That is the reality, but we are confident in the ability of the English club to remain in the top division.
"For now Ricky is only thinking about Sporting and helping them to get results. At the end of the season he will start to focus on Norwich."
Norwich currently 14th on the Premier League table, four points above the drop zone with five matches remaining.