Chelsea fear that Alvaro Morata could be ruled out for up to six weeks with a hamstring injury.
Morata started for the Blues against Manchester City in their 1-0 defeat on Saturday, but was substituted after just 35 minutes.
The striker was then withdrawn from the Spain squad for their upcoming World Cup qualifiers against Albania and Israel.
The Spanish football federation has confirmed that Morata underwent a scan on Monday, and a grade II myofascial injury in the hamstring was discovered. And that sounds bad.
Initial fears suggest that the 24-year-old could miss up to six weeks with the injury, and is almost certain to be sidelined for the rest of October.
Chelsea face Crystal Palace after the international break, with games against Watford, Everton, Bournemouth and two fixtures against Roma coming this month.
If the initial prognosis is accurate, the club’s record signing will also miss the game against Manchester United at Stamford Bridge on November 5.