Jonathan Woodgate is in talks with Newcastle after their £7m bid for the defender was accepted by Middlesbrough, reports BBC Radio Newcastle.
Woodgate has played 16 times for Middlesbrough this season
Woodgate, who left the Magpies to join Real Madrid in 2004, looks set for a return to the club having reportedly turned down a move to Tottenham.
Spurs had also had an offer for the England international accepted.
Woodgate, 28, was not included in Middlesbrough's squad for their FA Cup match at Mansfield on Saturday.
On Thursday, Boro manager Gareth Southgate insisted he was under no pressure to sell any of his players, although he confirmed on Saturday he has given permission to both Newcastle and Boro to speak to Woodgate.
"We wouldn't let anybody go unless we thought we were suitably covered in that position or had somebody else coming in who we thought could replace the player that was going," he said.
Southgate has other options in defence, with David Wheater, Robert Huth, Emanuel Pogatetz and Matthew Bates all competing for places.
Woodgate joined hometown team Boro for £7m from Real last summer, after an impressive campaign on loan from the Spanish club last season.