The Welsh winger picked up a grade 2 calf tear during the first half of Sunday’s Clasico against Barcelona and could be out for four weeks.
The injury also places Bale’s availability for the final in doubt – if Real make it past their neighbours – and could rule the Welshman out of the remainder of the La Liga season.
Bale’s inclusion in the starting line-up against Barcelona was a surprise, with the player only just recovered from a similar injury. And he lasted just 35 minutes before being withdrawn with an injury in his opposite leg.
Real Madrid manager Zinedine Zidane insisted that Bale was fit to play, saying "I'll never risk a footballer if he's not 100%."
But Bale’s setback is a big blow to Real Madrid’s chances of claiming a domestic and European double.
Read the full article on eurosport.co.uk: Injured Bale ruled out of Real Madrid's Champions League semi-finals