Spain star Isco was forced off in his country's friendly against Costa Rica after being caught on a late challenge.
The Real Madrid midfielder was levelled by a dangerous tackle from Ticos centre-back Kendall Waston, who was shown a yellow card in the 62nd minute for the challenge.
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Isco was attended to by Spain's medical staff but was unable to continue, with club team-mate Marco Asensio subbed on in his place.
The midfielder was, however, able to walk off the field, and Spain striker Alvaro Morata was optimistic after the game about his former Madrid team-mate's condition.
"It was a little thing," Morata is quoted as saying by AS. "Isco's leg had a knock, so let's hope he's well as soon as possible.
"Isco is a real phenomenon. This is his home, his land and as long as he is happy, we are happy."
Isco's name could be added to Madrid's growing list of injuries, with Mateo Kovacic, Keylor Navas, Raphael Varane and Gareth Bale all currently sidelined.
The Blancos face city rivals Atletico at the Wanda Metropolitano in the Madrid derby next Saturday, and losing Isco would be another blow for Zinedine Zidane's side.
Spain would go on to easily win the friendly 5-0, behind a double from David Silva.