Sunderland are believed to have reached a deal to sign French midfielder Yann M'Vila - in January.
The 26-year-old spent last season on loan at the Stadium of Light, and the Black Cats were keen to sign him permanently.
But Russian club Rubin Kazan have played hardball all summer over the fee.
M'Vila is out of contract in January, but Rubin have reportedly demanded £7million for his services.
Pictures were posted on social media showing M'Vila at Heathrow Airport with his agent.
He posted a message on his Instagram account saying: "I called Sunderland but they are not picking up the phone, why? My heart has broken."
The transfer window closed at 11pm without an immediate deal having been done.
However, it is understood Sunderland have reached a pre-contract agreement with the player for him to sign in January.