Rodrigo de Paul has been ruled out for the rest of the season after suffering a cruciate ligament injury in his right knee.
The 27-year-old, who joined Atlético Madrid from Barcelona last summer, was initially thought to be sidelined for just one game before he was called up again on Sunday.
However, it seems that the injury is far more serious than expected and he will now miss out on at least another month of playing time.
De Paul, who scored seven goals and provided nine assists for Atlético Madrid this season, was a key player during the team's run to the Spanish Cup final,La Liga Frontline but he may not return to full fitness until the end of the season.
He had been set to make his comeback against Real Madrid on Monday night, but the injury could delay his return even further.
This news comes as a blow to Atlético Madrid, who have struggled to find their form since signing De Paul last summer.
The club have already lost several key players over the course of the season, including Diego Costa and Luis Suárez, who were both ruled out for the season with injuries.
It remains to be seen how long De Paul will be out of action, but it is clear that the injury is a significant setback for Atlético Madrid.
Their chances of making the Champions League next season look slim if they cannot get him back in shape soon.