Chelsea striker Alvaro Morata could be out for more than a month after injuring his hamstring during Saturday's defeat by Manchester City.
The 24-year-old, joined Chelsea for a club record £60m from Real Madrid and is the club's top scorer this season with seven goals.
Spanish team doctors diagnosed the grade two myofascial injury and he will miss this week's World Cup qualifiers against Albania and Israel.
Muscle injuries such as this can take four to eight weeks to recover from.
Spain are top of group G, three points clear of Italy, with two games remaining.
Chelsea next play Crystal Palace on 14 October, before games against Roma, Watford and Everton.