Central to Gyökeres’s frustrations is a belief that he had an agreement with Sporting president Frederico Varandas to sell him for a certain fee, believed to be around €70 million (£60.4 million, $82 million). Varandas has publicly insisted Gyökeres will not be sold for such a price.

Arsenal are working to land Gyokeres and have a five-year deal prepared, subject to the clubs reaching an agreement over a fee.