After the tests carried out on Los Blancos captain Sergio Ramos by the Real Madrid Medical Services, he was diagnosed with tendinosis of the semimembranous muscle of his left leg
The defender only returned to the team for Wednesday's Champions League semi-final, second leg defeat to Chelsea but now looks set for another spell on the sidelines.
Real host Sevilla on Sunday evening as they attempt to reel in Atletico Madrid at the top of LaLiga.
Atletico have a two-point advantage entering the weekend's fixtures but they travel to third-placed Barcelona on Saturday afternoon with the outcome pivotal to the title outcome.
Ramos, 35, has been plagued by various injury issues this season and has featured in just 21 matches for Real. He also missed three matches after contracting Covid-19.
A club statement revealed his latest setback: 'Following the tests carried out by Sergio Ramos by the Real Madrid Medical Services, he has been diagnosed with tendonitis in the semi-membranous muscle of his left hamstring. His recovery will continue to be assessed.'
Ramos was powerless to prevent Real losing 2-0 to Chelsea in last Wednesday's second leg at Stamford Bridge, going down 3-1 on aggregate.
The injury comes at a time when his Real Madrid future is up in the air, with his present contract due to expire at the end of June.
Reports in Spain last week suggested that Ramos was willing to take a pay cut to secure a two-year contract extension but has so far only been offered a one-year deal.