The 33-year-old may quit the Bernabeu with Manchester United waiting to welcome him back with open arms.
Ronaldo is understood to be disgruntled at the Bernabeu after problems over contract demands with Florentino Perez.
The Portuguese superstar is reportedly upset that he is not on the same wage package that Lionel Messi and Neymar are on.
The player has already hinted at a move away, with Ronaldo’s comments putting Manchester United on red alert.
“It's been great being at Real Madrid,” he said after the Champions League final, which his side won 3-1.