Cenk Tosun is back at parent club Everton for tests on a knee injury, the PA news agency understands.
Tosun is reported to have suffered a serious knee problem while on loan at Crystal Palace.
The Turkey international will undergo medical examinations at Everton's Finch Farm base before the extent of the problem is known.
Tosun moved to Selhurst Park in January on a loan deal until the end of the season.
The 28-year-old has made two starts and three substitute appearances for Palace, scoring one goal in the 2-2 draw at Manchester City.
There is an option for Palace to sign Tosun permanently at the end of the season, but that move could be in jeopardy if the injury is serious, as could the player's participation at Euro 2020.