New Atletico Madrid signing Kevin Gameiro suffered a thigh injury in training on Wednesday, the club said.
Atletico signed Gameiro from Sevilla on a four-year contract last week for a reported fee of €32 million with add-ons in a deal that also saw Luciano Vietto head to Sevilla on loan.
The France forward injured his left adductor and has undergone an MRI scan to determine the extent of the damage, Los Colchoneros said in a statement.
The club said Gameiro would "receive physical therapy for the strain along with alternative therapies, and no timetable for his return has been set."
PARTE MÉDICO. @kevingameiro9 sufre una sobrecarga en el adductor largo del muslo izquierdo https://t.co/zvmMfN8jEi
- Atlético de Madrid (@Atleti) August 3, 2016
The France striker was not part of Les Bleus' Euro 2016 squad despite an impressive season with Sevilla, in which he won the Europa League for a third consecutive year.
He scored 67 goals for Sevilla, and his arrival was reported to have put an end to the possibility that Chelsea striker Diego Costa could return to Atletico.