Gareth Bale is a doubt for next month's Clasico against Barcelona after suffering an ankle tendon injury during Real Madrid's 2-1 Champions League win at Sporting CP on Tuesday, the LaLiga leaders have confirmed.
The Wales international limped off after 58 minutes in Lisbon having sustained a blow to his right ankle in a challenge with Sporting centre-back Sebastian Coates.
Tests conducted on Wednesday at University Hospital Sanitas La Moraleja showed Bale to have "a traumatic dislocation of the peroneal tendons in his right ankle".
Madrid did not put a time frame on the forward's recovery but he must now be considered a major doubt for this season's first Clasico showdown at Camp Nou on December 3.
Bale has been influential for Madrid this season, performing with distinction as Cristiano Ronaldo grappled with fitness problems post Euro 2016, scoring seven goals in 15 appearances across all competitions.
Zinedine Zidane's men are four points ahead of defending champions Barca at the top of LaLiga and host Sporting Gijon this weekend.
Alvaro Morata and Toni Kroos are also likely to miss out at Barcelona next month, although Zidane did enjoy a fitness boost when midfielder Casemiro returned to training following the trip to Portugal.
The Brazilian holding player has not featured since suffering a fractured fibula against Espanyol in September.