Sunderland are rivaling Rangers for Aston Villa defender Joleon Lescott.
The Daily Record says Rangers face competition from Sunderland with David Moyes also interested in signing the centre-back.
Lescott worked under Moyes at Everton for three seasons and his impressive displays secured him a £22million move to Manchester City.
But Moyes is said to be keen on reuniting with Lescott by bringing him to the Stadium of Light.
A source said: “(Mark) Warburton is well aware of the interest from Sunderland which is why he was so keen to travel south (Manchester) to have a proper conversation with Joleon, man to man.
“It's obviously difficult for a club with Rangers' resources to be competing for players against English Premier League clubs but sometimes the little things make a big difference.
“Clearly, Warburton wants to show Lescott how highly he is valued and how important he would be to the Rangers side."