Manchester United look to have been alerted after Real Madrid placed a cut-price valuation on top target Cristiano Ronaldo, according to Sport.
The 31-year-old has been linked with a sensational return to Old Trafford ever since the previous summer window, but newly appointed manager Zinedine Zidane is keen to see him remain at the club.
However, it is now believed that the forward will be considering his future at the Bernabeu in the summer, with Paris Saint-Germain also said to be keeping an eye on his situation.
With his contract set to expire in 2018, Real are hoping they can financially benefit from his sale before his price drops even more.
It is said that he is currently being valued at around the £48million region after enjoying huge success with the La Liga giants since his record breaking move from United back in 2009.
The Portugal international has once again been on amazing form, so far featuring 39 times in all competitions, scoring 42 goals while providing another 13 assists.