Titus Bramble is due to undergo a medical at Sunderland on Wednesday as the Black Cats attempt to tie up a deal for the Wigan defender.
Press Association Sport understands the Wearsiders were only given permission to speak to the 28-year-old former Newcastle player late on Tuesday night after the two clubs agreed a fee in the region of £1million.
Personal terms are yet to be finalised, but talks are ongoing and provided Bramble passes his medical, he could fly out to join up with the rest of Steve Bruce's squad in Portugal.
The Black Cats have wasted little time in pushing home their interest in Bramble after only making formal contact on Tuesday afternoon.
Even as late as Tuesday night after his side's 1-1 friendly draw at Oldham, Latics boss Roberto Martinez was playing down speculation that the central defender could be close to a move away from the DW Stadium.
Top target Heiko Westermann is destined to leave Schalke for Hamburg, while Bruce is still awaiting an answer from the honeymooning Sol Campbell following initial talks.
However, the former England international has several irons in the fire, including derby rivals Newcastle, and Sunderland are not allowing the grass to grow under their feet.
Ghana international John Mensah, who spent last season on loan from Lyon, remains in the frame, although his injury problems mean the Black Cats could not countenance a permanent move, and it remains to be seen whether a second short-term deal can be agreed.