Chelsea and Spain striker Alvaro Morata could be out for more than a month after injuring his hamstring during Saturday's 1-0 defeat to Manchester City.
The 24-year-old has returned to London to begin treatment after being diagnosed for a grade two myofascial injury by Spain team doctors.
Muscle injuries of this type can take four to eight weeks to heal.
He said in an Instagram post he later deleted on Tuesday he was targeting the game with Crystal Palace on 14 October.
Morata joined Chelsea for a club record £60m last summer from Real Madrid and is their top scorer this season with seven goals.