Real Madrid say the back injury that forced Cristiano Ronaldo off at half-time in the 1-1 Super Cup draw with Atletico Madrid is not a major concern.
The world player of the year, 29, was replaced by new signing James Rodriguez, who scored Real's goal.
Manager Carlo Ancelotti said: "Cristiano felt something and was uncomfortable. We'll evaluate it. He'll undergo all the checks and we'll see.
"It doesn't seem to be anything too serious."
Ronaldo played with knee and thigh injuries during the World Cup finals, where his Portugal side failed to get out of their group, but returned to score twice in Real's European Super Cup win in Cardiff last week.
Real face La Liga champions Atletico on Friday in the second leg of the Super Cup, a competition which pits the league champions against the Copa del Rey winners.
Real open their league campaign against Cordoba on Monday.