Portuguese news outlet Record has explained why that is the case, saying: "With Luis Suarez on his way to Sporting, Gyokeres is ready to head to Arsenal. The Lions accepted the Gunners’ offer on Wednesday, and since then, the clubs have been exchanging documents and reviewing formal aspects and legal issues, some of which are last-minute.
"This 'extension' postponed the 'officialisation' of the agreement for another day, contradicting the most optimistic prospects, which pointed to the deal being finalised yesterday."