Keegan is determined to sign an experienced central defender before the transfer window closes at the end of the month – and the 28-year-old is understood to be among his targets.

Woodgate left St James's Park three and a half years ago for Real Madrid, but his two seasons at the Bernabeu were wrecked by injury, and he returned to England to join his boyhood heroes Middlesbrough in August 2006, initially on loan.

And the Riverside Stadium club – who have repeatedly insisted Woodgate will not be leaving Teesside – could well have their resolve to hold on to him tested in the coming days.

Like Newcastle, Middlesbrough have struggled to make an impression on the Premier League this season, and this will have frustrated Woodgate, below.

And Keegan will be confident of selling a return to Tyneside to the defender.

Should Keegan's interest harden up into a firm bid, the England international may feel the time is right to return to St James's Park, where he had an 18-month spell after Sir Bobby Robson signed him from Leeds United in a £9m deal in January 2003.

However, Gareth Southgate and his chief executive Keith Lamb are determined to hang on to him.

Another issue is his injury record, and Woodgate – who has not featured for Southgate since New Year's Day – has been hit by cramp this season, missing Boro's last three games with the problem.

Meanwhile, United have sold out their 5,000-seat allocation for Saturday's FA Cup tie against Arsenal at the Emirates Stadium.

Fans had already snapped up the 3,000 tickets the club had been given for the Premier League fixture at the same venue four days later.