Sunderland are without a boss following Chris Coleman's sacking.
The market had gone cold as Sunderland await confirmation of Stewart Donald's takeover, with Chris Wilder frozen as most bookmakers' odds-on favourite for much of the past fortnight.
Then, on Friday last week, John O'Shea appeared at 7/1 with Paddy Power, to leave only Wilder and Michael Appleton (7/2) ahead of him.
McCarthy led Sunderland into the Premier League 13 years ago, and could be a popular choice among the Mackems faithful - some of whom called for his return after he parted company with Ipswich Town last month.
And while Cook has zero ties to Sunderland, his track record of promotions - three in four seasons - could make the 51-year-old another welcome appointment.
Who will be Sunderland's next manager?