The Daily Star says O'Neill wants to re-strengthen his side but needs to recoup some cash after a £40m summer spree.
Reo-Coker, once tipped for England honours, has had a stop-start career.
He won his place back in the side after a training ground bust-up with O'Neill which had led to him being suspended.
O'Neill insisted he was prepared to forgive and forget but it would seem the midfielder's chances of sticking around too long are limited.
Tottenham and Fulham are among clubs to be monitoring the situation.