The Black Cats have been one of the busiest teams during this month's transfer window, having snapped up goalkeeper Steve Harper, centre backs Lamine Kone and Jan Kirchoff, playmaker Wahbi Khazri and striker Dame N'Doye.
However, manager Sam Allardyce may not be done just yet, as with just a matter of hours to go until the transfer deadline, he allegedly wants to sign one of his most trusted players.
The Daily Mail report that Sunderland are trying to force through a late deal for West Ham defender Joey O'Brien, in a bid to add more new faces to their defence.
O'Brien, 29, worked with Allardyce at both Bolton Wanderers and West Ham, and is being targeted for another reunion with 'Big Sam', this time at the Stadium of Light.
The right back, who can also play at left back, has dropped down the pecking order at Upton Park since the signing of Sam Byram from Leeds United earlier this month, but an injury to Carl Jenkinson means that he may still be needed by Slaven Bilic.
It's suggested that West Ham are currently blocking a move from Sunderland for O'Brien, and this could be a move that runs right the way up to the deadline, as Allardyce pushes to work with O'Brien once again.
Would O'Brien be a good signing for Sunderland?