Stern John could return to haunt Coventry tomorrow if he makes his Sunderland debut against his old club.
The Trinidad and Tobago international joined the Black Cats from Coventry on Monday and could find himself lining up against his former team-mates at the Stadium of Light.
Coventry were initially keen to secure an agreement with Sunderland that John would not play against them tomorrow - but the Wearsiders rejected their request.
Sunderland boss Roy Keane said: "Coventry mentioned it but we were never going to agree to that.
"I suppose you can ask about those things but unless the buying club agrees then there is nothing you can do.
"I do not think it is right to stop a player playing and I would not do it."
John was not involved in Tuesday night's goalless draw with Crystal Palace as his registration documents had not come through in time. Sunderland missed out on a chance to break into the top six this week by dropping two points at home to Palace - but they will have another chance to move into the play-off places tomorrow.
Palace were clearly happy to play for a draw but Keane expects Coventry to come and attack.
He said: "Palace decided a point was a good result and, credit to them, they got it.
"Coventry come to us tomorrow on the back of a decent result and I think they will try and have more of a go at us.
"I try not to get too bogged down with what the opposition do though - it comes down to what we do on the day.
"It is another home game and we have to make sure we make them count now."
Former Sunderland assistant boss Adrian Heath is currently in charge of Coventry, who sacked Micky Adams last month.
Ex-Sunderland striker Kevin Kyle could make his return to Wearside after moving to the Ricoh Arena in August.
Keane will be without Liam Miller (hamstring) and Stanislav Varga (knee) but Stephen Elliott is likely to recover from the ankle injury which kept him out against Palace.
On-loan Manchester United right-back Danny Simpson could also make his debut tomorrow.