0715 GMT October 18, 2017
Bale arrived at the Santiago Bernabeu for a then world-record transfer fee from Tottenham, and he has enjoyed a trophy-laden spell with the Spaniards, The Daily Mail reported.
However his time has also been hindered by injuries, with the 28-year-old currently struggling with a left calf problem which saw him miss Wales' crucial 2018 World Cup qualifiers with Georgia and the Republic of Ireland.
And El Confidencial claimed on Tuesday that Bale is in a 'fight not to exhaust the diplomacy of [Zinedine] Zidane and the patience of Florentino [Perez]' due to his lengthy injury list.
The Spanish outlet added that Zidane 'knows that he is a player with whom he cannot count for a third of the season, at best'.
There are also concerns from the Spanish side that his love of golf — which he often plays when he has time off — contributes to Bale's back problems, it is reported.
It is understood that Real Madrid would consider parting ways with Bale, who has won three Champions Leagues in four seasons with the club, if Real can recoup the £86 million they paid Spurs to sign him over four years ago.
Manchester United manager Jose Mourinho is an admirer of the Welshman and has looked to bring him to Old Trafford in the past.
The Premier League giant was strongly linked with a move for Bale last summer but the Welshman opted to remain in Spain.
Bale has made 10 appearances for Zidane's men this season, scoring three goals.