The defender's move to Bristol City is hanging in the balance.
The position is something of a problem area for the Black Cats, with manager Sam Allardyce keen to add to it in the summer transfer window.
Last season he had DeAndre Yedlin in the role, but the American has returned to his parent club Tottenham Hotspur after his loan spell ended.
Sunderland are allegedly keen to have him back at the Stadium of Light, but so far have failed to strike a deal for either another loan deal or a permanent switch.
They had looked to be securing a deal for Inter Milan defender Davide Santon this week, before that deal fell through.
As a result, Adam Matthews must wait on his own future until the club can find the right-back they are looking for.
According to the Sunderland Echo, his move to Bristol City is hanging on the arrival of an alternative right-back, with Billy Jones the only other senior player in that position.
It now remains to be seen if they can do just that in the remainder of the summer transfer window.