Spain striker Fernando Torres lasted less than 16 minutes of Wednesday's World Cup qualifier against Belgium before being replaced by Cesc Fabregas.
Spanish media are reporting it was precautionary as the Liverpool striker had felt a tweak in the muscle in the back of his left leg.
Liverpool will be hoping it is not serious problem as they face Wigan and Chelsea in the Barclays Premier League next week, as well as a Champions League trip to Torres' former club Atletico Madrid.
Torres started the match well enough, firing in a 35-yard shot inside the opening two minutes that Belgium goalkeeper Stijn Stijnen needed to push away, but he was replaced not long after with the European Champions trailing 1-0 in Brussels.
pain team doctor Oscar Celada said on Spanish television: "He has intense pain in the back part of the thigh. It is difficult to diagnose now exactly the extent, if it is a question of a strain or a small tear.
"If it is a strain then he could be out for about a week.''