The club said its medical staff carried out scans after the midfielder reported pain in his left leg. Koke will train individually, with his progress determining when he can return to team training; Atlético have not confirmed a recovery date.
The injury comes during a congested spell for Diego Simeone’s side. Atlético are due to face Espanyol, Stuttgart and Deportivo over the next 10 days, before travelling to Alavés and hosting Bayern Munich and Barcelona in two high-profile fixtures later in the year.
The Barcelona match on 9 November has been identified as a possible target for Koke’s return, although that remains uncertain until the club provides a clearer assessment of the injury.
Koke’s absence would leave Simeone without his captain during a demanding sequence of domestic and European matches. The 34-year-old remains an important presence in midfield, combining experience with his understanding of the manager’s demands.
Atlético have several options in the centre of the pitch, but the depth chart has its own concerns. Pablo Barrios and Johnny Cardoso have both had injury problems in the past, while Morten Hjulmand, who began the campaign as a starter, has since lost his place.
Cardoso is also a concern ahead of the Espanyol match after missing training with acute gastroenteritis, adding to the selection issues in midfield.
The injury arrives during a difficult personal period for Koke, whose mother recently passed away. He received support from supporters earlier in the week, and the club will now monitor his recovery while preparing for a demanding stretch of fixtures. Marca reported that the club’s medical update offered no fixed timetable, leaving his availability for the November programme dependent on his rehabilitation.
Atletico Madrid have not yet specified how many matches their captain could miss. His return will depend on how the muscle responds to treatment and when he is able to resume training with the group.